ABSTRACT Lexically, 52.99% of the Tibeto-Burman languages, the non-Sinitic branches of the Sino-Tibetan language family, treat fog as something identical or similar to cloud, based on our

database of 234 Tibeto-Burman varieties; there are three lexical relations of such fog-cloud similarity in Tibeto-Burman languages, namely cloud colexified with fog, cloud as a hypernym of

fog, and cloud as a formative of fog. The rest of the Tibeto-Burman languages use semantically disconnected words to describe fog and cloud. The high proportion of fog-cloud similarity in

Tibeto-Burman languages, compared with that of the non-Tibeto-Burman languages spoken alongside the Trans-Himalayan region (i.e., 10.80%, a result based on our database of 213

level. After reviewing the meteorological features, it is found that the Tibeto-Burman region has ideal conditions for the formation of low cloud, namely with high humidity and through

orographic uplift due to the mountainous environment. Since Tibeto-Burman speakers live in high elevations, low cloud, the dominant cloud of the region, may surround them or beneath their

view. Therefore, they may find it difficult or not necessary to distinguish fog from low cloud. Our conclusion is also supported by the languages of other families and regions, such as the

Daghestanian languages of the Caucasus region and the languages of the Central Andes. Moreover, the present findings agree with the theory of efficient communication. That is, languages

displaying fog-cloud similarity are adaptive to higher elevations with less communicative need to distinguish between the two concepts by using completely different and unrelated linguistic

forms; on the contrary, languages displaying fog-cloud divergence have stronger need to do so, resulting as well from their adaptation to the extra-linguistic environment. Finally, tropical

climates, another possible predictor for fog-cloud similarity, are identified as a future research direction. SIMILAR CONTENT BEING VIEWED BY OTHERS A REVISED DIGITAL EDITION OF WURM &

HATTORI’S LANGUAGE ATLAS OF THE PACIFIC AREA Article Open access 29 August 2024 A COMPARATIVE WORDLIST FOR INVESTIGATING DISTANT RELATIONS AMONG LANGUAGES IN LOWLAND SOUTH AMERICA Article

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November 2023 INTRODUCTION Fog is a cloud resting near the ground; both are aggregates of tiny water droplets or ice crystals suspended in the air (Ahrens, 2012). The difference between fog

and cloud is nothing physical but height only. Since clouds are normally high up in the sky and may not disrupt visibility, different from fog that appears near the ground level and can

impact daily life, many cultures treat them as different weather events. This is reflected in the use of semantically disconnected words to describe fog and cloud in their languages, such as

“cloud” and “fog” in English, and “nuage” and “brouillard” in French. However, some cultures may experience and perceive fog and cloud as identical or similar weather events. They colexify

fog and cloud in their languages, namely, they use the same lexical form for two functionally distinct meanings (François, 2008, p. 170). There are 183 cases of fog-cloud colexification in

the database of Cross-Linguistic Colexifications (or CLICS) (Rzymski et al., 2020), such as Blang (Austroasiatic) m̥ut2 ‘cloud, fog’, Lezgian (Nakh-Daghestanian) tsif ‘cloud, fog’, and Enga

(Nuclear Trans New Guinea) mulupána ‘cloud, fog’. 123 of the 183 languages, or about 67%, belong to 5 language families in CLICS. One of them is the target family of the present research:

the Tibeto-Burman languagesFootnote 1. In the present study, we examine the fog and cloud words of the Tibeto-Burman (TB) languages, namely the non-Sinitic branches of the Sino-Tibetan

language family (Jacques, 2015). A large number of TB languages, or about 53% in our database of 234 Tibeto-Burman varieties, do not lexically treat fog and cloud as differently as languages

like English and French. Some TB languages colexify fog and cloud, such as zdam ‘fog, cloud’ in Re’ela Qiang (Qiangic) (Zhou, 2019) and t͡ʃa̠m31thɔi35 ‘fog, cloud’ in Maru (Burmish) (Huang,

1992; Wen, 2022). Some consider fog a hyponym of cloud, such as sazdiə̂m (ground:cloud) ‘fog’ (cf. zdiə́m ‘cloud’) in Situ rGyalrong (Qiangic) (Zhang, 2020). In some other TB languages,

although fog is expressed with a different morpheme, cloud must be a formative of the fog expression, e.g., dəLɹɥɛ̃H (cloud:fog) ‘fog’ in Niuwozi Prinmi (Qiangic) (Ding, 2014). The three

relations are called in this study fog-cloud similarity (cf. fog-cloud divergence in section “Data classification”). Admittedly, there is a phylogenetic reason for fog-cloud similarity in TB

languages since they evolved from the common ancestral Proto-Tibeto-Burman (PTB). For example, the fog and cloud words in the above-mentioned Re’ela Qiang, Situ rGyalrong, and Niuwozi

Prinmi all retain Proto-Tibeto-Burman *s-dim ‘cloud, fog’ (Matisoff, 2003). But this leads to the query: why did Tibeto-Burman languages start to exhibit fog-cloud similarity even at the

early stages? Moreover, fog and cloud words in TB languages have multiple etymons. In our database, the fog and cloud expressions can at least be encoded by and traced to eight reconstructed

PTB words by Matisoff (2003). Other than *s-dim, the other seven are *r-məw ‘sky, heavens, clouds’, *muːŋ/*r/s-muːk ‘foggy, dark, sullen, menacing, thunder’, *kəw-n/t ‘smoke’, *bwar/*pwar

‘fire’, *m-ka-n ‘heavens, sky, sun’, *mway ‘cloud, fog’, and *siŋ/*sik ‘wood, firewood, tree’. Similar reconstructions are also found in other sources, such as Benedict (1972), Bradley

(1979), Coblin (1986), LaPolla (1987), and VanBik (2009). However, *bwar/*pwar and *mway are not found in cases of fog-cloud similarity, namely not acting as a shared morpheme, which encodes

cloud and fog in our TB database. Their reflexes can refer either to fog or cloud, but not both. For example, PTB *bwar/*pwar ‘fire’Footnote 2 is the proto-form of the italicized morpheme

in Jingpho (Brahmaputran) sai33_wan__31_ ‘fog’, with a semantic change from ‘fire’ to ‘fog’ (see Burling, 1983; So-Hartmann, 1988), but not used in the cloud words in our database. PTB *mway

‘cloud, fog’ is used in either cloud words or fog words, but not both, of mainly the Kuki-Chin-Naga languages, such as Tiddim mei2 ‘cloud’, Khumi tmáay ‘fog’, and Hakha mǐn-_mây_ ‘cloud’

(VanBik, 2009). Although both share the reconstructed meaning of ‘cloud’, the exact relation between PTB *mway ‘cloud, fog’Footnote 3 and *r-məw ‘sky, heavens, clouds’Footnote 4 remains

unclear. However, while *r-məw is mainly found as a formative of cloud and fog words in Burmo-Qiangic, Macro-Tani, and Himalayish languages, *mway ‘cloud, fog’ is mainly used in

Kuki-Chin-Naga languages. Besides *s-dim, mainly found in Burmo-Qiangic languagesFootnote 5, the other five common etymons (italicized in examples) which are involved in fog-cloud similarity

are *r-məw ‘sky, heavens, clouds’, e.g., doŋ_muk_ ‘fog, cloud’ in Bokar (Macro-Tani) (Huang, 1992; Sun, 1993), *muːŋ/*r/s-muːk ‘foggy, dark, sullen, menacing, thunder’, e.g., _muk˥_pa˥

‘fog, cloud’ in Cangluo Monpa (Bodic) (Zhang, 1986; CASS, 1991), *kəw-n/t ‘smoke’, e.g., mi55_k__h__ɔ̪__31_ ‘smoke, cloud, fog’ in Yangliu Lalo (Burmo-Qiangic) (Yang, 2010), *m-ka-n

‘heavens, sky, sun’, e.g., zdeʔm ‘cloud’ and zdeʔm._caʔ_ (cloud:sky) ‘fog’ in Kyom-kyo rGyalrong (Burmo-Qiangic) (Prins, 2016; Nagano and Prins, 2013), and *siŋ/*sik ‘wood, firewood, tree’,

e.g., tɕɯ˧ ‘cloud’ and tɕɯ˧_sɯ˧˥_ ‘fog’ in Yongning Na (Burmo-Qiangic) (Michaud, 2018). PTB *r-məw and *muːŋ/*r/s-muːk should share a common etymological origin, or have an allofamic

relationship, but have developed to the modern languages through different routes (see Matisoff, 2003; Benedict, 1972; LaPolla, 1987). Therefore, here comes the second query: why do multiple

etymons in TB languages, even though ‘cloud’ and ‘fog’ may be the derived meanings from the reconstructed meanings (e.g., ‘sky’, ‘smoke’, and ‘firewood’), end up exhibiting fog-cloud

similarity? The present study aims to seek the underlying reason and answer the following research question: what predicts fog-cloud similarity in Tibeto-Burman languages, other than the

phylogenetic relation? The hypothesis is that languages spoken at higher elevations are more likely to exhibit fog-cloud similarity. We will also use the findings to explain the

colexification of the non-Tibeto-Burman data in CLICS. LITERATURE REVIEW The present study joins the discussion of the influence of the natural environment upon linguistic expressions, which

has been a prolific subject of study in the last three decades. There are two major forces in the literature to support linguistic adaptation to ecological conditions. The primary force is

the study of the phonetic and phonological patterns (e.g., Munroe et al., 1996, 2009; Munroe and Silander, 1999; Fought et al., 2004; Ember and Ember, 2010; Maddieson, 2012, 2018; Maddieson

and Coupé, 2015; Coupé and Maddieson, 2016; Everett et al., 2015; Everett, 2017). Notwithstanding the less impact, perhaps due to smaller sample sizes or less sophisticated algorithms, the

lexicon is another main linguistic subsystem, which posits such a relationship with the natural environment (e.g., Witkowski and Brown, 1985; Levinson, 2003; Levinson and Wilkins, 2006;

Burenhult and Levinson, 2008; Baddeley and Attewell, 2009; O’Meara and Pérez-Báez, 2011; Palmer, 2015). Discussion from the structural perspective was occasional, e.g., Nichols (1992),

although the studies of the influence of other extra-linguistic factors on grammatical structures have been continuous, such as the cultural factors and social factors (e.g., Dunn et al.,

2011; see a review in De Busser, 2015). The lexical perspective, as the theme of the present study, is not new in itself and can be found as early as in Boas’s (1911) observation about the

words for snow in Eskimo languages (see follow-up discussion in Martin, 1986 and Pullum, 1991) and Sapir’s (1912) indication of the “stamps” of the physical environment borne by the

vocabulary of a language. With the development of diverse linguistic databases, such as The World Loanword Database (WOLD) (Haspelmath and Tadmor, 2009) and Intercontinental Dictionary

Series (IDS) (Key and Comrie, 2015), and the availability of more library references, the environmental impact on the lexicon has gained more attention. For example, Regier et al. (2016)

revisited the snow and ice words in the languages of the world and found that languages, which colexify snow and ice tend to be spoken in warmer climates. In other words, people in warmer

climates have lower communicative need to distinguish snow and ice. Recently, a series of interdisciplinary studies have looked into the use of verbs in weather expressions (Dong et al.,

2020, 2021; Huang et al., 2021). A hypothesis has been proposed by such studies that weather events with bigger weather substances and faster weather processes tend to select action verbs of

high transitivity. It has successfully accounted for the selection of verbs in Sinitic weather expressions, e.g., frost is more inclined to use transitive verbs than fog, which is lighter

than frost, and the wind expressions using verbs meaning ‘to hit’ all describe strong wind such as typhoon, which moves much faster than ordinary wind. Concerning the present hypothesis that

languages spoken at higher elevations are more likely to exhibit fog-cloud similarity, two works by Urban (2012, 2023) have also addressed the similar relationship between elevation and the

lexical use of fog and cloud, by analyzing the global dataset of IDS and a self-assembled dataset of South American languages. His general finding is that the mean elevation of the

languages colexifying fog and cloud is higher than that of the non-colexifying languages (Urban, 2012, 2023). The present study investigates this correlation using different data and

methods. Firstly, while Urban (2012, 2023) examined the phenomenon with a focus on the languages of the Central Andes in South America, the present study utilizes data from the

Trans-Himalayan region in Asia. The Central Andes feature high elevations and the tropical climate of the Amazon rainforest ecoregions, and both of these environmental variables can affect

the lexical use of fog and cloud (see section “Application to CLICS data”). The Trans-Himalayan region, on the other hand, does not feature the tropical climate and we can better observe the

impact of elevation. Secondly, the Tibeto-Burman languages in the present study, or the non-Sinitic branch of the Sino-Tibetan family (or the Trans-Himalayan family), were estimated to be

formed around 6000 BP or even earlier, followed by migration and expansion covering topographically and climatically diverse areas (Domrös and Peng, 1988; Shi, 2018; Zhang et al., 2019;

Sagart et al., 2019). This time depth is much longer than the languages in the Central Andes, such as Quechuan and Aymaran, which may have evolved around two millennia (Urban, 2023).

Therefore, with a longer phylogeny, the Tibeto-Burman languages may have adapted to the environment more effectively, thus allowing us to examine the correlation between the environment and

language with higher certainty. Lastly, Urban’s (2012, 2023) findings are based on the “strict colexification” of fog and cloud, namely the exactly same lexeme in synchrony (François, 2008,

p. 171), such as gõy ‘cloud, fog (as well as smoke)’ in Maxakalí, a Nuclear-Macro-Je language in Brazil (Popovich and Popovich, 2005). Differently, the present study samples the data based

on both “strict colexification” and “loose colexification” (François, 2008, p. 171), including not only the same lexeme in synchrony but also lexemes which share etymologically related form

or exhibit derivational/compounding relationships, such as sazdiə̂m (ground:cloud) ‘fog’ and zdiə́m ‘cloud’ in Situ rGyalrong (Qiangic) (Zhang, 2020). By doing so, we can further ground our

study into the theory of efficient communication and similar theorizing (Gabelentz, 1901; Bates and MacWhinney, 1982; Du Bois, 1985; Rosch, 1999; Croft, 2003; Haiman, 2010; Regier et al.,

2015, 2016). According to Regier et al. (2015, 2016), to support efficient communication, the semantic systems in world languages tend to achieve a near-optimal tradeoff between

informativeness and simplicity. The former supports precise communication and the latter minimizes cognitive effort. If a language fulfils its communicative need by strictly colexifying two

senses, or “strict colexification”, the cognitive effort is the least. However, different languages employ different solutions, which are rated as efficient (Regier et al., 2015). “Loose

colexification”, like “strict colexification”, is also a potential means of minimizing cognitive load, e.g., sharing related forms makes communication cognitively easier than using

completely unrelated distinguishing lexemes (see Finley, 2018; Xu et al., 2020), such as ‘cloud’ and ‘fog’ in English. ABOUT TIBETO-BURMAN LANGUAGES Whether Tibeto-Burman is a proper

subgrouping under Sino-Tibetan/Trans-Himalayan hypothesis is still controversial (e.g., van Driem, 2007; Jacques and Michaud, 2011). Therefore, we do not use _Tibeto-Burman_ in the present

study in a subgrouping sense, but only as a term to refer to non-Chinese Sino-Tibetan languages (Jacques, 2015). The Tibeto-Burman languages comprise about 475 languages spoken across a wide

geographic range, or the Tibeto-Himalayan region, mainly in the Hengduan Mountains of southwest China, the Qinghai-Tibet plateau, the Yunnan-Guizhou plateau, Myanmar (formerly Burma), and

countries in or beyond the Himalaya, such as Bangladesh, India, Bhutan, Nepal, and Pakistan. The Tibeto-Himalayan region is high in elevation. For example, the average elevation of the

Qinghai-Tibet plateau is around 4000 m above sea level; topographically, the Hengduan Mountains, which are to the southeast of the Qinghai-Tibet Plateau, are among the most rugged mountains

of the world (Muellner-Riehl, 2019). Due to the ruggedness, biodiversity is promoted, as well as cultural and linguistic diversity (Gorenflo et al., 2012; Axelsen and Manrubia, 2014).

Hammarström et al. (2022) classify the TB languages into 17 branches, except the extinct Nam language. The largest three branches are Burmo-Qiangic (158 languages), Kuki-Chin-Naga (87

languages), and Bodic (82 languages). More than half of the 17 branches have only 1 to 3 languages, such as Gongduk (1), Digarish (2), and Kman-Meyor (2). Moreover, Tibeto-Burman languages

have a history of about 6000 years, whose speakers migrated south from the upper reaches of the Yellow River valley into the eastern edge of the Qinghai-Tibet plateau, according to the

estimation of the Sino-Tibetan split at the time of the Yangshao Neolithic culture (Zhang et al., 2019). Zhang et al. (2019) also estimate that the initial Tibeto-Burman divergence time,

i.e., 4665 years BP, occurred in the middle period of the Majiayao culture, which derived from the Yangshao culture, in eastern Gansu, eastern Qinghai, and northern Sichuan, China. Evidence

can still be found in the traditional folklore of the Tibeto-Burman language speakers. For example, speakers of Central Prinmi in Yunnan, a Qiangic language in southwestern China, believe

that they are not indigenous to Yunnan, but were originated from an area bordering Qinghai and Gansu to the north of their current home; they also believe that their ancestors led a nomadic

life and traveled south until they reached the present-day region between southwestern Sichuan and northwestern Yunnan (Yan and Wong, 1988; Ding, 2014). Tibeto-Burman languages are

typologically diverse, containing both isolating languages (e.g., Lolo-Burmese languages) and synthetic languages (e.g., rGyalrongic and Kiranti languages). All TB languages are SOV except

the Karenic and Baic branches which are SVO. Most TB languages place modifiers after the noun, although preposed modifiers can also be found (Dryer, 2008). Matisoff (1990, 2003) considers

the highly tonal, monosyllabic, and analytic TB languages as the result of Sinospheric influence, and the marginally tonal or atonal TB languages with complex systems of verbal agreement

morphology as the result of Indospheric influence. While some TB languages are in one or the other, others have been influenced by both Chinese and Indian cultures. The linguistic features

in Table 1 show that while Meithei and Tibetan are more Indospheric, Naxi and Lahu are more Sinospheric; Qiang and Prinmi show mixed features of both. DATA COLLECTION The fog words and cloud

words were collected from 234 Tibeto-Burman languages or dialects from China, Bhutan, Bangladesh, Myanmar, Nepal, and India. They cover 11 branches of the TB languages: Burmo-Qiangic (142),

Bodic (33), Kuki-Chin-Naga (16), Himalayish (11), Brahmaputran (11), Macro-Bai (5), Macro-Tani (5), Nungish (4), Kho-Bwa (3), Digarish (2), Dhimalish (1), and Kman-Meyor (1). The sources of

data are mainly descriptive grammars, print dictionaries, and three databases: The Sino-Tibetan Etymological Dictionary and Thesaurus (or STEDTFootnote 6), rGyalrongic Languages

DatabaseFootnote 7, and The Data Collection, Recording, and Display Platform for the Chinese Language Resources Protection Project (or DCRDCLRFootnote 8). As basic words, expressions for fog

and cloud are widely recorded in the sources and their morphological structures can often be clearly analyzed based on the information provided by the sources. We examined all the instances

of the fog and cloud words in each source, including the word list and, if available, their usage in phrases and clauses, before we input the form and meaning in our database. We also

consulted the relevant part of the reference grammars to understand the morphology of the words when necessary. All the words were cross-checked, wherever possible, by another source(s) of

the same variety (e.g., different print references, and the audio files and annotations in DCRDCLR). Typologically, the data can also be cross-checked by the forms of words with the same

meaning in varieties of the same language branch. All the data were double-checked after collection (see “Data availability”). For the purpose of comparison, the fog words and cloud words

from another 213 languages or dialects were also collected. They are the non-Tibeto-Burman languages, spoken alongside the Trans-Himalayan region which, as defined by Jacques (forthcoming),

is a vast area from Baltistan in the West to the Shandong peninsula in the East, and Inner Mongolia in the North down to Myanmar in the South. The comparative languages are spoken at diverse

elevations, from as low as 1 m, such as Shenzhen Hakka (Sinitic) in Guangdong, China, to as high as over 3000 m, such as Tajik (Indo-European) in Xinjiang, China. Moreover, the comparative

languages represent a high level of linguistic diversity, with a multitude of discrete languages from varied phylogenetic families, covering synthetic (e.g., Indo-European and Turkic) and

analytic (e.g., Hmong-Mien) varieties, similar to the TB sample languages. Lexical data from 10 language families were collected (see Fig. 1): Austroasiatic (15), Austronesian (8), Dravidian

(4), Hmong-mien (26), Indo-European (12), Mongolic-Khitan (13), Sinitic (72), Tai-Kaidai (42), Tungusic (7), and Turkic (14). The data were also mainly taken from descriptive grammars,

print and online databases/dictionaries (e.g., DCRDCLR and Austronesian Basic Vocabulary DatabaseFootnote 9). To extract the elevation data, we first identified the fieldwork sites or

dialectal localities of the data from the references. Then the addresses were searched in Google Earth. To improve accuracy, we recorded the elevations of the data points within 100 m in

Google Earth. We also used the coordinates in Glottolog and CLICS, if we cannot identify the exact dialectal localities in the references. We also extracted the data of annual relative

humidity (RH) from Wikipedia when they are available, since an important condition of cloud formation is water vapor or moist air (Ahrens, 2012). Relative humidity is measured by “the ratio

of the amount of water vapor in the air to the maximum amount of water vapor required for saturation” (Ahrens, 2012, p. 87). There are 336 RH data obtained out of the 447 sample languages,

specifically 162 RH data in the Tibeto-Burman languages and 174 in the comparative languages. DATA CLASSIFICATION It is oversimplified to treat fog and cloud as different words by merely

looking at their lexical forms. While it is easy to make decision about the fog words and the cloud words from 1 to 6 in Table 2 since they are identical, accounting for 32.48% of our TB

data, and those from 7 to 12 since they are completely different, accounting for 47.01% of our TB data, morphological and etymological analysis is needed to classify the data such as from 13

to 18, accounting for 20.51% of our TB data. The fog words and the cloud words share a morpheme from 13 to 18 in Table 2. Most of the shared morphemes in Table 2 are reflexes of PTB *s-dim

‘cloud, fog’ (Matisoff, 2003), such as rGyalrong (Situ) _zdiə́m_ ‘cloud’ and sa_zdiə̂m_ ‘fog’, and Prinmi (Niuwozi) _dĩ__H_ ‘cloud’ and _də__L_ɹɥɛ̃H ‘fog’. Additionally, it is possible for a

language to use more than one word for either cloud or fog. Therefore, our classificatory criterion is: a language displays fog-cloud similarity as long as it can express ‘fog’ and ‘cloud’

with identical forms or its fog and cloud expressions share the morpheme, which encodes the fog or cloud event. This criterion spares us from being distracted by any complex lexical system

for cloud and fog in a particular language. For example, Sherpa (Bodic) distinguishes between shrīn ‘high cloud’ and mūkpa ‘low cloud’. And Sherpa is a case of fog-cloud similarity since

mūkpa colexifies ‘fog’ and ‘low cloud’ (Hale, 1973; Tournadre et al., 2009). Lahu (Lolo-Burmese) is another example. Although it has various lexical expressions for different types of cloud

and fog, as long as we know that ‘cloud’ and ‘fog’ can be expressed identically as mò (Matisoff, 2006), it can be concluded that Lahu displays fog-cloud similarity, or specifically a case of

fog-cloud colexification. GuiyangFootnote 10 Mandarin has two words for ‘fog’, namely in31u24 (cloud:fog) ‘fog’ and u24tsau24 (fog:covering) ‘fog’ (Wang, 1994). In Guiyang Mandarin, the fog

word in31u24 (cloud:fog) contains the cloud morpheme in31 ‘cloud’, though the other fog word u24tsau24 (fog:covering) does not. Since the morpheme which encodes the cloud event is shared by

the fog and cloud words, the language is also treated as a case of fog-cloud similarity. Spoken at an elevation of 1274 m, Guiyang Mandarin is the only Sinitic variety of fog-cloud

similarity in our database (see section “Higher elevation and fog-cloud similarity”). It is relatively easier to categorize the fog and cloud data as being identical forms and completely

different forms. Our focus of the following subsections is on the further sub-categorization of the morpheme-sharing cases. Most of these languages are Burmo-Qiangic, and some are Bodic and

Macro-Bai. We have found two major structural relations among them: (1) the cloud morpheme is the head of the fog word, and the other morphemes are modifiers. In this case, fog is understood

as a kind or a hyponym of cloud, such as Situ rGyalrong zdiə́m ‘cloud’ and sazdiə̂m ‘fog or ground cloud’; and (2) the cloud morpheme is not the head of the fog word, and it may be a

modifier of the fog morpheme or its coordinate. In this case, fog is not a kind or a hyponym of cloud, such as dĩH ‘cloud’ and dəLɹɥɛ̃H (cloud:fog) ‘fog’ in Niuwozi Prinmi, and in31 ‘cloud’

and in31u24 (cloud:fog) ‘fog’ in Guiyang Mandarin. It is also discovered most Tibeto-Burman languages use more complex morphological structures for fog, often based on the cloud morphemes.

The word formations of the fog words are through derivation and compounding (modification and coordination). Some cases can be found where the cloud word is based on the fog morpheme. In

Yangliu Lalo and Mangdi Lalo, both Lolo-Burmese varieties under the Burmo-Qiangic branch, the cloud words, namely mi55khɔ̪31 and mi55kɨ21 respectivelyFootnote 11, are formed based on ‘fog’

mi55 and ‘smoke’ khɔ̪31/kɨ21 (Yang, 2010). FOG IS A KIND OR A HYPONYM OF CLOUD When the cloud morpheme is the head of the fog word in the word formation, fog is understood as a hyponym of

cloud. FOG IS “GROUND CLOUD” Cross-linguistically, it is common for fog to be called literally as “ground cloud”, such as Bonan (Mongolic-Khitan) ɢɑdʑir mokə (ground cloud) ‘fog’ (Ding,

2022) and Pnar (Austroasiatic) lʔɔʔ kʰn̩daw (cloud ground) ‘fog’Footnote 12 (Nagaraja et al., 2013). In our Tibeto-Burman data, as is exemplified by rGyalrong (Situ) in Table 2, the fog word

is compounded with two nominal formatives: sa and zdiə́m. The former is a reflex of PTB *(s/z)a-y ‘earth, ground, soil, sand’ and the latter PTB *s-dim ‘cloud, fog’ (Matisoff, 2003), hence

literally “ground cloud” (see Table 3). FOG IS “DARK/MUDDY CLOUD” As is exemplified by Khroskyabs (Wobzi) in Table 2, the fog word is compounded through the cloud morpheme and a postposed

morpheme meaning ‘dark or black, muddy’, hence literally meaning ‘dark cloud’ or ‘muddy cloud’ since most Tibeto-Burman languages place the modifier of property after the head noun. This

pattern is also found in Qiangic, such as dámù̥ (cloud:dark) ‘fog, cloud’ in Longxi Qiang and dámò (cloud:dark) in Mianchi Qiang (Evans, 1999; Zheng, 2016), and rGyalrongic languages (see

Table 3), and Lolo-Burmese languages (e.g., Ninglang Lisu) (see Table 3). The rGyalrongic modifying morphemes mean ‘dark, black’, all of them being reflexes of Proto-Tibeto-Burman *s-ma(ŋ/k)

/ *s-nak ‘ink, black, deep’, reconstructed by LaPolla (1987) and Matisoff (2003). Lisu morpheme xua̠33 means ‘muddy’ (Li, 2022a); but its source is not clear. FOG IS “PREFIX-CLOUD” Again,

in rGyalrongic languages, the prefix kə- is probably historically related to the velar nominalization prefix, reconstructed as *gV-. See a cross-linguistic discussion of the PTB prefix *gV-

in Konnerth (2016). Its functions in rGyalrongic languages, as well as other TB branches (e.g., Kuki-Chin-Naga and Brahmaputran), include derivational nominalization and clausal

nominalization (see Sun, 2014; Nagano, 2017; Jacques, 2021). Specifically, the prefix kə- should create gerund nominalization for the fog expression of the rGyalrongic varieties in Table 3,

literally meaning ‘being cloudy’. FOG IS “CLOUD-SUFFIX” There are two major types of suffixes in our TB data, namely the reflexes of PTB nominalizer *-pu / *-pwa and of PTB gender suffixes

(Benedict, 1972; Matisoff, 2003). It is a common derivation in Bodic languages to express ‘cloud’ and ‘fog’ with the nominalizer (italicized), such as mu:_pa_ ‘fog’ in Kaike (Hale, 1973) and

tʂĩ55_pə__55_ ‘cloud’ in Lhasa Tibetan (Huang, 1992). In our TB data, the suffix -mbə31 in nDrapa (Burmo-Qiangic) ʂti35_mbə__31_ (cloud-nominalizer) ‘fog’ should be a borrowing from the

Tibetic language (Huang, 2020). Since the stem ʂti35 of the fog word is a reflex of PTB *s-dim ‘cloud, fog’, the core meaning of the derived word is not changed. Regarding the gender suffix,

Honkasalo (2019: p. 225) points out that Eastern Geshiza rGyalrong zdo-ma ‘cloud’ borrows the suffix _-ma_ from Tibetan, related to the historical feminine suffix (also see Matisoff, 1991).

The rGyalrong suffixes _-mo/-mu/-wo_ in Table 3 should all be the gender suffixes. While _-mo/-mu_, similar to Eastern Geshiza _-ma_, are probably based on the Tibetan feminine nominal

suffix _-mo_, _-wo_ is from the Tibetan masculine nominal suffix _-po_. FOG IS “V-ING CLOUD” This formation involves the use of the cloud formative and a verbal formative. In Menglang Lahu

(Lolo-Burmese), the morpheme fei1 in the fog word mu2fei1 means ‘to cover something up’, semantically similar to the verb fı̂ʔ in Black Lahu (Matisoff, 2006). Therefore, literally, fog in

Menglang Lahu means ‘covering cloud’. This kind of N-V compounding is also found in Qiangic languages. For example, in Ronghong Qiang, zdə.qhu (cloud:descend) refers to ‘fog’ and zdɑm to

‘cloud’ (LaPolla and Huang, 2003); similarly, in Mawo Qiang, zdɤ.qu (cloud:descend) means ‘fog’ and zdɤm ‘cloud’ (Liu, 1998). Therefore, in Ronghong and Mawo Qiang, the meaning of ‘fog’ is

literally “descending cloud”. Nouns formed via N-V compounding are popular in TB languages, such as meɹgu̥ ‘thunder’ < me:ɹ ‘sky’ + gu ‘to thunder’ in Ronghong Qiang (LaPolla and Huang,

2003, p. 332). UNIDENTIFIED MODIFYING MORPHEME It is sometimes unable to identify the origins of some modifying morphemes, but decision can still be made about their sub-categorization. For

example, the source of the morpheme ʑø35 in Shade Muya (Burmo-Qiangic) ʑø35ndɯ33ʐe35 ‘fog’ is unknown, where ndɯ33ʐe35 refers to ‘cloud’ (CASS, 1991); bo33 in Ersu (Burmo-Qiangic) bo33tsɛ55

‘fog’ is unclear about its source, where tsɛ55 refers to ‘cloud’ (CASS, 1991). Since the morpheme preceding the cloud word is not found to be a coordinate, but either a nominal modifier or a

prefix in our sample TB languages, the cloud morpheme is highly likely to be the head of the compounding and fog is as well a kind of cloud. It is suspected that ʑø35 in Shade Muya and bo33

in Ersu are both loanwords from Southwest Mandarin, namely ʑø35 is related to Southwest Mandarin jy53 ‘rain’ and bo33 Southwest Mandarin po21 ‘thin’. Regarding the former, cognitively, it

is possible for people to use water-related concepts to refer to fog (see section “Fog is ‘cloud water’”). Regarding the latter, when an adnominal modifier is borrowed, it is common for the

borrowed Chinese adjective/stative verb to be used before the head noun. For instance, in Liangshan Yi, with which Ersu has frequent contact, the first morpheme ta55 of the word ta55ga33

(big:road) ‘big road’ is a loanword from Southwest Mandarin ta213 ‘big’, although there is an inherent expression ga21mo21 (road:big) ‘(big or main) road’ in Liangshan Yi. FOG IS NOT CLOUD,

BUT INVOLVES CLOUD Unlike the hyponym-hypernym relation of fog and cloud in section “Fog is a kind or a hyponym of cloud”, cloud is not the head morpheme of the word formation, but a

modifier or a coordinate component of the fog word. It is also observed that TB languages commonly relate fog to other concepts in these expressions, such as ash, smoke, and dew. FOG IS

“CLOUD ASH” In Dechang and Yongsheng Lisu, the second morphemes (italicized in examples) of the fog words, namely mu44 and m̩44, refer to ‘ashes, dust’, such as na44tshɿ31_mu__44_

(medicine:ash) ‘medicine powder’ and ʃa44_mu__44_ (wheat:ash) ‘flour’ in Dechang Lisu (Li, 2022b), and na44tshɿ42_m̩__44_ (medicine:ash) ‘medicine powder’ and dza33_m̩__44_ (grain:ash)

‘flour’ in Yongsheng Lisu (Li, 2022c). It is common to find in other languages of the world the colexification of ‘ashes, dust’ and ‘fog’/‘cloud’, such as Wabula Cia-Cia (Austronesian) gaβu

‘dust, fog’ (Kaiping et al., 2019), Buyang (Tai-Kadai) la0muk11 ‘dust, fog’ (Key and Comrie, 2015), and Bukusu (Atlantic-Congo) fuumbi ‘dust, cloud’ (Greenhill and Gray, 2015). In

Tibeto-Burman languages, Burmese (written) mru also displays this kind of colexification, namely ‘minute particle; mist, fog’ (Benedict, 1976). This type of compounding is also identified in

Naic and Bodic languages but with possible semantic extension. In Naxi and Yongning Na (Narua) (see Table 4), two Naic languages, the first morphemes of the fog words, namely tɕi31 and

tɕɯ˧, refer to ‘cloud’; the second morphemes sɯ33 and sɯ˧˥ are reflexes of PTB *si(ŋ/k) ‘wood, firewood, tree’ or PST *siŋ ‘wood, firewood, tree’ (Chou, 1972; LaPolla, 1987; Matisoff, 2003).

This diachronic relation is also consistently found in synchronic Naic data between ‘fog’ and ‘firewood’, such as Dayan Naxi tɕhi55sɚ33 ‘fog’ and sɚ33 ‘firewood’ (Zhao, 2022), and Yanbian

Naxi tsɿ21sɿ33 ‘fog’ and sɿ̠33 ‘firewood’ (Liu, 2022). There should be a further semantic extension of the second morpheme from ‘firewood’ to ‘ash’, probably via an intermediate connection

with ‘charcoal’Footnote 13. The path of semantic development from ‘charcoal’ to ‘ash’ is also typologically attested by Sunwar (Himalayish) koylā: ‘charcoal, ash’ (Hale, 1973), and Botlikh

(Nakh-Daghestanian) кьей ‘charcoal, ash’ (Key and Comrie, 2015). FOG IS “CLOUD SMOKE” In Luquan Lisu (see Table 4), the fog word is formed by the formative ti33 ‘cloud’ and khə31/khe31

‘smoke’ (Mu and Sun, 2012), where the former is a reflex of PTB *s-dim ‘cloud, fog’ and the latter a reflex of PTB *kəw-n/t ‘smoke’. Therefore, there is a connection between smoke and fog in

Luquan Lisu. Some languages colexify fog and smoke, such as Batsbi (Nakh-Daghestanian) k'ur ‘fog, smoke’ (Carling, 2017) and Rongga (Austronesian) nuː ‘fog, smoke’ (Kaiping et al.,

2019). FOG IS “CLOUD DEW” In Bai, the fog word vã42kõ̱21 is formed with the formative ‘cloud’ and ‘dew’. Although the fog expression must contain the cloud morpheme in Bai, some languages

can colexify dew and fog with identical forms, such as Wancho (Brahmaputran) rangphum ‘dew, fog’ (Marrison, 1967), and Romani (Indo-European) bruma ‘dew, fog’ (Key and Comrie, 2015). FOG IS

“CLOUD SKY” Fog expression in rGyalrongic languages (see Table 4) can also be formed by compounding PTB *s-dim ‘cloud, fog’ and PTB *m-ka-n ‘heavens, sky, sun’, such as rGyalrong (Kyom-kyo)

zdeʔm.caʔ (cloud:sky) ‘fog’, rGyalrong (Xiaojin Zhailong) zdem.kʰɑ (cloud:sky) ‘fog’, and rGyalrong (Lixian Ganbao) zəŋ.kʰe (cloud:sky) ‘fog’ (Nagano and Prins, 2013). Since both formatives

are nominals, the cloud morpheme is not the head of the fog word, but a modifier. Fog thus literally means “cloud sky”. FOG IS “CLOUD WATER” In Pengbuxi Muya, the fog word _ndɛ__33_tɕhʌ53

shares the cloud morpheme (italicized) with the cloud word _ndə__33_ʐe53. The other morpheme tɕhʌ53 is a variant of the word tɕʌ53 ‘water’ in Muya, which may become aspirated in compounding,

namely ndɛ33tɕhʌ53. Associating ‘fog’ with water is also found in Sinitic languages, such as Liuzhou Mandarin (Sinitic) u24suɐi54 (fog:water) (Liu, 1995) and Dongguan Yue (Sinitic)

mɔu32sui35 (fog:water) ‘fog’ (Zhan et al., 1997). This connection also conforms to the physical properties of fog as a form of water (Day, 1998; Ahrens, 2012). FOG IS “CLOUD STEAM” In

Shuizhuping Lalo, the fog word is compounded with the cloud morpheme ti24 and the steam morpheme kv̩21 (see Table 4) (Yang, 2010). Colexification of steam and fog is commonly attested in

other languages, such as Romanian (Indo-European) abur ‘steam, fog’, and Otomi (Otomanguean) 'bipa ‘fog, steam’ (Haspelmath and Tadmor, 2009). FOG IS “CLOUD AND FOG” This formation is

through coordinate compounding of the cloud morpheme with the fog morpheme, namely ‘fog’ < cloud + fog, such as Prinmi (Niuwozi) dəLɹɥɛ̃H. The fog morphemes in our database have diverse

etymons. For example, the fog morphemes in the PrinmiFootnote 14 varieties and Qiang are probably cognate with le ‘fog’ in Tangut, the extinct Qiangic language (see Li, 1997 and Table 4).

Tangut le is still kept in χde33le33 (cloud:fog) ‘fog’ of Taoping Qiang, a southern Qiang dialect. In Manshuiwan Yi, the fog morpheme vu55, probably a Southwest Mandarin loanword, is

lexicalized to be part of the cloud word mu33vu55 (cloud:fog) ‘cloud’; the fog word is expressed with an additional fog morpheme mu33vu55vu55 (cloud:fog) ‘fog’. In this kind of formation,

there is a specific morpheme for fog; and cloud, not being the head of the compounding, is a formative of the fog expression. In other words, cloud may be considered a necessary component of

fog in these cultures. SUMMARY After the morphological analysis, four types of data are identified in the database. For the first type of data, fog is cloud, identically, such as Lizu,

tɕe53 ‘fog, cloud’ (Huang, 1992). This type of data displays fog-cloud colexification. For the second type of data, fog is also cloud, but with modifications, acting as cloud’s hyponym, such

as zdiə́m ‘cloud’ and sazdiə̂m (ground:cloud) ‘fog’ in rGyalrong (Situ). For the third type of data, fog is not cloud, but involves the concept of cloud, such as dĩH ‘cloud’ and dəLɹɥɛ̃H

(cloud:fog) ‘fog’ in Prinmi (Niuwozi). For the last type of data, fog is completely different from and unrelated to cloud, such as ti33 ‘cloud’ and mu33ȵo55 (sky:fog) ‘fog’ in Liangshan Yi.

The first three types of data are called fog-cloud similarity in the present study, and the fourth type is fog-cloud divergence. We processed the non-Tibeto-Burman data in the same way. See

the distribution of fog-cloud similarity and fog-cloud divergence of the sample languages in Fig. 2. Due to the lack of lexical and morphological information, there are five TB data points

in our collection, which we cannot further sub-categorize, namely Maram Naga (Kuki-Chin-Naga) _kamong_ ‘cloud’ and _kamong_-sole ‘fog’ (Marrison, 1967), Puroik (Kho-Bwa) _kə__33__tɯ__33_ and

_kə__33__tɯ__33_sɯ33 (CASS, 1991), Gyaru Manang (Bodic) _mɯʔ__2_pa2 ‘cloud’ and _mɯk__2_sɯl2 ‘fog’ (Nagano, 1984), Mianning Namuyi (Burmo-Qiangic) _tʂu__33_ ‘cloud’ and _tʂu__33_tɕhi33xo35

‘fog’ (CASS, 1991), and Tuoqi Prinmi _də__13_rõ53 ‘cloud’ and _də__13_rẽ55 ‘fog’ (Lu, 2001). Although whether they should be sub-categorized as the second or third type remains undetermined,

it is still safe to conclude that these data points show fog-cloud similarity since the cloud morpheme (italicized above) is contained in the fog word. The first two lexical relations,

namely fog-cloud colexification and fog as a hyponym of cloud, form the core of fog-cloud similarity since there is no specific word for fog. The third type, i.e., cloud as a formative of

fog, can be considered as the transitional layer from core fog-cloud similarity to fog-cloud divergence since there comes a specific morpheme for fog. It is also noted that fog-cloud

similarity in Tibeto-Burman languages is mostly concentrated to the southeast of the Qinghai-Tibet plateau (see the dotted square in Fig. 2). RESULTS AND DISCUSSION In this section, we will

discuss the environmental influence, the hypothesized underlying reason besides the phylogenetic relations, for fog-cloud similarity in Tibeto-Burman languages. It is also found that

language contact is a major reason for relatively recent fog-cloud similarity and divergence. Finally, we will apply our findings to the colexification data in the database CLICS. HIGHER

ELEVATION AND FOG-CLOUD SIMILARITY In our database, fog-cloud similarity accounts for 52.99% of the Tibeto-Burman languages, but only 10.80% of the non-Tibeto-Burman data. The TB and non-TB

data also suggest that languages displaying fog-cloud similarity have higher average and median elevations than fog-cloud divergence languages. See Table 5. We ran a Two-Sample t-Test in

Excel. The result shows that the elevations of fog-similarity languages are significantly different from those of fog-cloud divergence languages. Similar findings were reported in Urban

(2023) by using the IDS and Central Andean data of “strict colexification”. Meanwhile, the range of elevation is also narrower in fog-cloud similarity languages than in fog-cloud divergence

languages, suggesting that fog-cloud similarity is least likely to occur in some elevations. The top four ranges of elevation where fog-cloud similarity is found in TB languages are from

1000–1500 m, 1500–2000 m, 2000–2500 m, and 2500–3000 m (see Fig. 3). If the elevation is lower than 500 m or higher than 3500 m, fog-cloud similarity is unlikely to occur. This observation

is also valid if only the core fog-cloud similarity TB languages and all the TB and non-TB data are considered. This is a main different discovery from Urban (2023): in his study,

colexifying languages were spoken at both low and high elevations; in other words, there are fewer restrictions on the distribution of colexification, which is in contradistinction to the

findings in Regier et al. (2016). On the contrary, the present study supports Regier et al. (2016). That is, the colexifying languages are more strongly constrained than the diverging

languages with regard to the non-linguistic variables, temperature in Regier et al.’s (2016) snow-and-ice case and elevation in the present fog-and-cloud study. To account for the

discrepancy, Urban (2023) ascribed to lineage-specific preferences, namely a language family can be consistently colexifying, such as the Quechuan family, or consistently differentiating,

such as the Aymaran family. Our results partly agree with the lineage-specific account: the lineage-specific preference can be observed at the lower end of the family tree. In our samples,

the three largest branches of the Tibeto-Burman languages, namely Burmo-Qiangic, Kuki-Chin-Naga, and Bodic, feature both fog-cloud similarity languages and divergence languages, showing

little evidence of intra-lineage effect at such higher-level nodes. For example, 35.97% of the Burmo-Qiangic samples distinguish fog and cloud with completely unrelated forms, and 35.25%

strictly colexify fog and cloud. Similarly, both strictly colexifying and completely differentiating languages are found in the Bodic branch, with 25% of the former and 71.9% of the latter.

Most of the diverging languages within the Bodic branch at very high elevations, above 3000 m, come from the Tibetan varieties, showing the lineage-specific effect at the lower-level node.

But the lineage-specific effect may not be at play at other lower-level nodes. For example, in our non-TB samples, both strictly colexifying and completely differentiating languages are

found in Miao (Hmongic) and Bouyei (Kam-Tai). Among the 12 Miao varieties, the only two colexifying fog and cloud are located at the elevations of 1431 m and 1722 m, while the other ten

differentiating fog and cloud with unrelated forms average 701.1 m, ranging from 351 m to 1086 m. The only colexifying Bouyei has the highest elevation among the three Bouyei varieties in

our samples, namely 2107 m versus 1094 m and 1275 m. Besides, we examined the locations of the Central Andean colexifying data below 500 m in Urban (2023) and found that all of them fell

within the Amazon rainforest ecoregions featuring the tropical climate. Instead of a lineage-specific preference, the colexification of fog and cloud in these languages is probably the

result of adaptation to the tropical climate, which is another extra-linguistic variable for this phenomenon (see section “Application to CLICS data”). Additionally, people opt to settle

down at lower elevations (Nogués-Bravo et al., 2008), namely, there should be more languages spoken in lower areas. Even given this correlation between settlement distribution and elevation,

however, fog-cloud similarity still shows robust relations with higher elevations. In other words, the number of languages of fog-cloud divergence decreases as elevation increases, showing

a general settlement tendency; however, the distribution of fog-cloud similarity is not related to the settlement pattern (see Fig. 3). A MIXTURE OF LOW CLOUD AND FOG Fog-cloud similarity is

most likely to occur between elevation 1000 m and 3000 m in the Tibeto-Burman area. Two kinds of cloud also occur in this range in the middle-latitude region, or the subtropical and

temperate zones (cf. the tropical zone in section “Application to CLICS data”), namely the low cloud (0–2000 m) and midlevel cloud (2000–7000 m) (Ahrens, 2012, p. 103). Liu et al. (2018) and

Wei et al. (2020) indicate that the southeast of the Qinghai-Tibet plateau, the hotspot of fog-cloud similarity (see Fig. 2), is heavily overcast, with annual total cloud cover up to 69.5%,

due to the high relative humidity by moisture transport from the Bay of Bengal. The average annual relative humidity of the places where we found fog-cloud similarity is 67.87%, ranging

from 42% in Shannan, Tibet, China, to 80% in Lianghe County, Dehong Dai and Jingpo Autonomous Prefecture, Yunnan, China. Moreover, low cloud is the dominant cloud in this area, with an

annual low cloud cover of 51.9% (Wei et al., 2020). According to Walcek (1994), cloud cover is positively correlated with the relative humidity of a region. Similarly, a high level of low

cloud cover can also be found in the southern slope of the Himalaya due to the monsoon, and the frequency of cloud coverage can exceed 75% at 15 Local Solar Time in the monsoon period

(Jaswal et al., 2017; Kattel et al., 2013; Kurosaki and Kimura, 2002). Comparatively, since the west of the Qinghai-Tibet plateau is more arid, it has less cloud cover: its annual total

cloud cover and annual low cloud cover are 49% and 30.5%, respectively (Wei et al., 2020). Liu et al. (2018) also indicate that in the southeast of the Qinghai-Tibet plateau, the most

frequent low clouds are stratus and nimbostratus. According to US National Oceanic and Atmospheric Administration (NOAA) and Ahrens (2012, p. 105–106), the former, abbreviated as St, is a

low greyish cloud layer with a fairly uniform base; at lowland, a stratus cloud often resembles a fog that does not touch the ground and fog is a surface-based form of stratus cloud.

Normally, there is no precipitation falling from the stratus. The latter, abbreviated as Ns, is a dark gray, wet-looking cloud layer; it is often associated with more or less continuously

falling rain or snow. Therefore, frequent contact with low cloud suggests that it is not easy or not necessary for the Tibeto-Burman speakers to distinguish low cloud from fog. When low

clouds occur in their highland environment, whose frequency is high (Wei et al., 2020), they have different experience with the clouds from people living near the sea level. Liu et al.

(2018) point out that the major reason for low cloud formation in the Tibeto-Burman region, such as the southeast of the Qinghai-Tibet plateau, is due to orographic uplift. Orographic uplift

is defined by NOAA as a phenomenon to occur when horizontally moving air is forced to rise before they go through a large obstacle, such as hills or mountains. The forced lifting due to the

topographic barrier results in cooling, another important condition for cloud formation. If the air is humid and the cooling is sufficient, water vapor condenses into clouds. Due to

orographic uplift, the low cloud may float on the mountaintop or just around the waist of the mountains. The residents who live there can treat the low cloud differently from the lowland

people. While the lowland people see the low cloud above them, the mountain people often see the low cloud around them or beneath them (see Fig. 4). Additionally, regarding the comparative

non-Tibeto-Burman data, even though these languages are spoken in areas where the average relative humidity (74.29%) is higher than that of the Tibeto-Burman region, without the orographic

uplift caused by the rising elevation, people’s perception of low cloud can be completely different. CONTACT-INDUCED FOG-CLOUD SIMILARITY AND DIVERGENCE By looking at the proto-forms, some

TB languages have maintained fog-cloud similarity (e.g., rGyalrongic languages) and divergence (e.g., Lolo-Burmese languages) for a long time. But some TB varieties display more recent

changes through lexical borrowing. Due to the contact, they have gained or lost fog-cloud similarity or divergence. For example, while the other rGyalrongic languages keep using the PTB

cloud morpheme *s-dim for both cloud and fog, some rGyalrongic varieties borrowed the fog word from Old Tibetan smug-pa and thus lost fog-cloud similarity. The fog word in rGyalrong (Aba

Rongan Menggucun), rGyalrong (Maerkang Ribu), and rGyalrong (Rangtang Puxicun) are sməkpe, smək̚pe, and smək̚pa, while their cloud words are zdim, zdjəm, and zdo, respectively (Nagano and

Prins, 2013). Since fog and cloud are common weather phenomena, the borrowing occurs because of the prestige of the source language, rather than any need of naming new items. Within the

Trans-Himalayan region, Tibetan culture is among the most influential ones, especially in the Tibeto-Burman area, hence the borrowing from Tibetan to rGyalrong. The Tibetan influence also

reached non-Tibeto-Burman languages. For example, Tongren Bonan and Jishishan Bonan, two Mongolic varieties spoken in Qinghai and Gansu, China, both borrowed the words for fog and cloud from

Amdo Tibetan, directly or indirectly. While Jishishan Bonan, with an elevation of 2485 m, spoken in Jishishan Bonan, Dongxiang and Salar Autonomous County, Linxia, Gansu, China, displays

fog-cloud similarity, namely mokə ‘cloud’ and ɢɑdʑir mokə (ground cloud) ‘fog’ (Ding, 2022), Tongren Bonan, with an elevation of 1955 m, spoken in Tongren County, Huangnan Tibetan Autonomous

Prefecture, Qinghai, China, differentiates ʂən ‘cloud’ from mukuɑ ‘fog’ (Bai, 2022). Due to the influence of Tibetan culture, different varieties of Bonan can either have fog-cloud

similarity or fog-cloud divergence after borrowing from the prestigious language. Other examples of borrowing concern another prestigious group of languages: the Sinitic languages. For

example, while Bijiang Bai, a Northern Bai dialect with an elevation of 1808 m, spoken in Yunnan, China, colexifies fog and cloud, namely mɯ21ko42 ‘fog, cloud’ (CASS, 1991), Baishi Bai,

another Northern Bai dialect with an elevation of 2278 m, spoken in Yunnan, lost fog-cloud similarity after borrowing the Chinese word y35 from the local Southwest Mandarin: y35 ‘cloud’ and

mɯ35kɔ42 ‘fog’ (Yang, 2014). Furthermore, Lianghe Achang, a Burmish language in Dehong, Yunnan, China, with an elevation of 1301 m, gained fog-cloud similarity through language contact. It

borrowed u33lu33 (fog:dew) from the local Mandarin to colexify fog and cloud; it is also fine to use u33 without the dew morpheme for ‘fog’ in Lianghe Achang (Shi, 2009). In Chinese

languages, it is common to use wu51lu51 (fog:dew) or its variants for ‘fog’, such as in Yantai Mandarin, Yudu Hakka, Danzhou Cantonese, Pingxiang Gan, and Ningbo Wu. Unlike Lianghe Achang,

Luxi Achang, a close dialect of the former, with an elevation of 958 m, also borrowed u55lu35 from local Mandarin for ‘fog’, but does not replace its cloud word na55mau55 (sky:cloud) ‘cloud’

(Dai and Cui, 1985). Our data also suggest that languages prefer differentiating once they have the linguistic and cultural impetus to do so. There are more contact-induced cases of

fog-cloud divergence languages than of fog-cloud similarity languages in our samples. In other words, language contact chiefly promotes differentiation. This observation supports Regier et

al.’s (2016) asymmetric pattern that there is a general preference for informative and precise communication. APPLICATION TO CLICS DATA There are 183 cases of fog-cloud colexification in

CLICS, including 33 TB languages. After we gained the necessary geospatial information (e.g., location and elevation) of the data in CLICS and removed the repetitive data points and all TB

data, there are 131 varieties left, from 34 language families. The average elevation of fog-cloud colexification data in CLICS is 983.3 m, lower than the TB data, but still much higher than

the average elevation (526.4 m) of the fog-cloud divergence languages of our non-TB sample languages (see Table 5). This means that elevation remains to be a difference between languages of

fog-cloud similarity and those of fog-cloud divergence. Our conclusion, namely fog-cloud similarity is more likely to occur at higher elevations, is supported by 46 languages/dialects in

CLICS, or 35.1%, which are used at elevations ranging from 1000 m to 3000 m. The 46 languages are mainly from Austroasiatic, Camsá, Mpur, Kunza, Indo-European, Barbacoan, Nuclear Trans New

Guinea, Austronesian, Timor-Alor-Pantar, and Daghestanian families. For example, the 34 Daghestanian languages stand out with an average elevation of 1758.1 m and a median elevation of

1713.5 m, spoken in the rugged mountainous Caucasus region. However, while some Nuclear Trans New Guinea and Austronesian languages support our conclusion, which are spoken at high

elevations, such as Kobon (2671 m) and Pazeh (2514 m), some are used at low elevations, such as Bima (15 m) and Apali (121 m). It seems to be a challenge to our conclusion that 51

languages/dialects of fog-cloud colexification are spoken below the elevation 500 m in CLICS (average 211 m), a range which is the least likely for fog-cloud similarity to occur, according

to our TB and non-TB data. The table in Fig. 3 shows that only 4 languages in our sample displaying fog-cloud similarity are below elevation 500 m, all from the non-Tibeto-Burman samples.

After we checked the distribution of the 51 languages/dialects from CLICS, 46 of them, or 90.2%, are located in East Nusa Tenggara (Indonesia), Timor-Leste (or East Timor), Papua New Guinea,

and Amazon rainforest ecoregions (see Fig. 5). These areas happen to feature tropical climates, characterized by year-long high temperatures, high humidity, and high precipitation (Beck et

al., 2018; Galvin, 2016). Galvin (2016, p. 28) indicates that the cloudiest tropical zone stretches across the central Indian Ocean, Indonesia, and Malaysia to New Guinea. Therefore, rather

than being a challenge to our conclusion, this observation of colexification below 500 m points to another probable environmental predictor for fog-cloud colexification: the tropical

climate. This also explains the colexifying languages in the low elevations in Urban (2023), which are spoken in the Amazon rainforest ecoregions in South America (see Fig. 5). Besides high

humidity, the lowland tropical zone also has the condition to cool the water vapor, though not through orographic uplift as in the Tibeto-Burman region. Atkinson (2002) points out that

stratus cloud is common along the tropical coasts where warm moist air is advected over cool coastal waters. After the stratus cloud is cooled, it may reach the water or ground surface.

Moreover, advection fog can also be formed by warm moist air moving over a colder surface and cooling to its saturation point (Ahrens, 2012, p. 98). This kind of environment provides the

cognitive conditions for people to mix low cloud with fog. This may explain the fog-cloud colexification in languages along the coasts of East Nusa Tenggara and Timor-Leste. Papua New Guinea

and the Amazon basin also belong to the tropical zone. But they have a tropical rainforest climate, different from the tropical savanna climate of East Nusa Tenggara and Timor-Leste (Beck

et al., 2018), resulting in a different mechanism for cloud/fog formation. The trees and other plants in the rainforest transpire vast amounts of water vapor from their leaves and release

tiny particles serving as cloud condensation nuclei, around which water droplets condense to form clouds and eventually rain (Pöhlker et al., 2012; Fenning, 2014). According to Obregon et

al. (2014), lowland rainforests also feature frequent occurrence of ground-touching clouds, which are in contact with the forest canopy and are perceived as fog at the surface. Therefore,

due to the frequent formation of fog/low stratus cloud, this type of rainforest is called “tropical lowland cloud forest” (Gradstein et al., 2010; Obregon et al., 2011; Gehrig-Downie et al.,

2012). Interestingly, since fog and cloud are very hard to distinguish in tropical lowland rainforests, Obregon et al. (2014, p. 322) propose the use of the term “lowland fog forest” as a

synonym for “lowland cloud forest”. In sum, cases of lowland fog-cloud similarity, specifically fog-cloud colexification, in the database of CLICS and Urban (2023), do not contradict our

conclusion by the Tibeto-Burman languages. On the one hand, many colexification languages in CLICS support our conclusion. On the other hand, those which do not corroborate are actually

pointing to another predictor for fog-cloud similarity, i.e., the tropical climate. It is worth future investigation with expanded sample languages in the tropical zone. CONCLUSIONS The goal

of the present study is to investigate the influence of natural environment upon linguistic expressions, specifically the influence of elevation upon the lexical use of fog and cloud in

Tibeto-Burman languages. After studying 234 Tibeto-Burman languages/dialects and comparing them with 213 non-Tibeto-Burman languages in the Trans-Himalayan region, it is found that more than

half of the Tibeto-Burman languages display fog-cloud similarity, and it is more likely to happen at higher elevations, particularly between the range of 1000 to 3000 m. The high proportion

(i.e., 52.99%) of fog-cloud similarity in Tibeto-Burman languages, compared with that of the non-Tibeto-Burman languages (i.e., 10.80%), shows that languages are adaptive to ecological

conditions. There are three lexical relations for fog-cloud similarity in Tibeto-Burman languages. While some Tibeto-Burman languages colexify fog and cloud, some consider fog a hyponym of

cloud, using the cloud morpheme as the head with other modificatory morphemes. In some other Tibeto-Burman languages, although fog is expressed with a different morpheme or related to a

different concept (e.g., ash, dew, smoke), cloud must be a formative of the fog expression, though not as the head; in other words, cloud is part of the fog. The other half of the

Tibeto-Burman languages use semantically disconnected words to describe fog and cloud. After reviewing the meteorological features, we found that the Tibeto-Burman region has the ideal

conditions for the formation of low cloud, mainly the stratus and nimbostratus cloud. Firstly, it is very humid. Secondly, its topography can cool the moist air. When the horizontally moving

moist air runs into the topographic barrier, the high elevation forces it to rise and cool, and the moist air eventually condenses into clouds, a process called orographic uplift. Since

Tibeto-Burman speakers live in high elevations, low cloud, the dominant cloud of the region, may surround them or beneath their view. Therefore, they may find it difficult or not necessary

to distinguish fog from low cloud. Moreover, our findings support Regier et al.’s (2016) theory of efficient communication. The fog-cloud similarity languages, including both strict and

loose colexification, are more constrained than the fog-cloud divergence languages with regard to the non-linguistic variable, namely elevation in the present study. It suggests that

languages displaying fog-cloud similarity are adaptive to higher elevations with lower communicative need to distinguish between the two concepts by using completely different and unrelated

linguistic forms. On the contrary, fog-cloud divergence languages have stronger need, resulting from the physical environment, to communicate by using completely different concepts and thus

different linguistic forms. Furthermore, we have identified other factors than the physical environment, playing their roles in the lexical use of “fog” and “cloud” among the Tibeto-Burman

languages, namely the lineage-specific preference, and the effect of language contact. At the lower nodes of the family tree, some closely related varieties can, not necessarily though,

display the lineage-specific effect, such as the Tibetan. But the lineage-specific effect is not found at higher nodes of the family tree. Contact-induced cases of fog-cloud similarity and

divergence are also found. After borrowing from prestigious languages (e.g., Tibetan and Chinese), close dialects or varieties can behave differently regarding their lexical use of fog and

cloud. Meanwhile, language contact promotes differentiation since there are more contact-induced cases of fog-cloud divergence than of fog-cloud similarity in our samples. The result is

confirmative of Regier et al.’s (2016) asymmetric pattern, which suggests that there is a general preference for informative and precise communication. Therefore, the causal link between

higher elevation and fog-cloud similarity should not be treated as deterministic, but probabilistic. Parallel to Regier et al.’s (2016) findings based on ice and snow, not all languages at

high elevations will necessarily collapse the fog and cloud distinction. A probabilistic stance indicates that there is less communicative need to preserve the distinction between fog and

cloud at higher elevations and there is higher communicative need to distinguish them at lower elevations. Finally, our conclusion, namely fog-cloud similarity is more likely to occur

between the elevation 1000 and 3000 m, is supported by 46 languages/dialects, or 35.1%, in CLICS. Instead of being a challenge to our conclusion, the CLICS data and Urban’s (2023) samples of

lowland languages below elevation 500 m point to another predictor for fog-cloud similarity, i.e., the tropical climate, which is a direction for future investigation. DATA AVAILABILITY The

datasets generated during and/or analyzed during the current study are available in the Dataverse repository: https://doi.org/10.7910/DVN/S6PTEJ. NOTES * CLICS uses the term “Sino-Tibetan”.

But since there are no Sinitic languages in this database, the “Sino-Tibetan” languages in CLICS are all Tibeto-Burman. * Similar reconstructions to PTB *bwar/*pwar ‘fire’ in Matisoff

(2003) are *bwár / *pwár in Benedict (1972) and *bar in Coblin (1986). The reflexes of this etymon are mainly verbs, such as par ‘to burn’ in Apatani (Macro-Tani) (Sun, 1993), and bar ‘to

burn (intransitive)’ and par ‘to burn (transitive)’ in Kanauri (Bodic) (Benedict, 1972). But many of its reflexes in Brahmaputran languages are nouns, such as wan31 ‘fire’ in Jingpho (Liu,

1984) and wal ‘fire’ in Garo (Burling, 2003). * VanBik (2009) and Mortensen (2012) reconstructed ‘cloud, fog’ of Proto-Kuki-Chin as *may and of Proto-Tangkhulic as *moj, respectively,

consistently featuring the nucleus as complex vowels. * Matisoff’s (2003) reconstruction *r-məw is similar to Benedict’s (1972) *(r-)muw and Weidert’s (1987) *(r-)məw / *(r-)muw. * For

example, many Loloish (or Ngwi) cloud words are descendants of *s-dim or Proto-Loloish *C-dim1, reconstructed by Bradley (1979). * Accessed at https://stedt.berkeley.edu/. * Accessed at

https://htq.minpaku.ac.jp/databases/rGyalrong/lang/index.php?langindex=eng. * The Chinese name of the database is 中国语言资源保护工程采录展示平台. Accessed at https://zhongguoyuyan.cn/index.html?lang=cn. *

Accessed at https://abvd.eva.mpg.de/austronesian/. * Guiyang, the capital city of Guizhou Province, southwest China, has an average annual relative humidity of 77 % (Chen et al., 2021) and

was the most humid city in China in 2020, according to https://www.statista.com/statistics/282491/china-annual-average-humidity-in-major-cities/. * According to Yang (2010), mi55 should be a

reflex of PTB *muːŋ ‘foggy, fog’. * According to Ring (2015), when both formatives are nouns, noun compounds in Pnar are functionally genitival expressions, such as ka=balaŋ lɑthɑdlɑbɔt

‘Lathadlabot church’ or ‘church of Lathadlabot’, where ‘church’ is the head. * There is another possible, but less likely, interpretation of the semantic formation of ‘fog’ in Naic

languages, namely literally “cloud smoke”. Although it is possible for the colexification to occur between ‘fog’ and ‘smoke’ (see section “Fog is ‘cloud smoke’”), typologically, the

connection between ‘firewood’ and ‘smoke’ is not attested. Due to a lack of intermediate connection between the two meanings, therefore, we are more confident to propose the semantic

development from ‘firewood’ to ‘ash, dust’. * In Pumi, nasal vowels are very widespread, some of which originated in nasal codas (Michaud, Jacques and Rankin, 2012). REFERENCES * Ahrens CD

(2012) Essentials of meteorology: an invitation to the atmosphere, 6th edn. Brooks/Cole, Belmont Google Scholar  * Atkinson GD (2002) Forecasters’ guide to tropical meteorology. University

Press of the Pacific, Honolulu HI Google Scholar  * Axelsen JB, Manrubia S (2014) River density and landscape roughness are universal determinants of linguistic diversity. Proc Biol Sci

281(1784):1–8. https://doi.org/10.1098/rspb.2013.3029 Article  Google Scholar  * Baddeley R, Attewell D (2009) The relationship between language and the environment: information theory shows

why we have only three lightness terms. Psychol Sci 20:1100–1107 Article  PubMed  Google Scholar  * Bai A (2022) Qinghai Tongren Bao’anyu (Tongren dialect of Bonan in Qinghai).

https://zhongguoyuyan.cn/point/65779. Accessed 23 Dec 2022 * Bates E, MacWhinney B (1982) Functionalist approaches to grammar. In: Wanner E, Gleitman L (eds) Language acquisition: the state

of the art. Cambridge University Press, New York, pp. 173–218 Google Scholar  * Beck H, Zimmermann N, McVicar T et al. (2018) Present and future Köppen-Geiger climate classification maps at

1-km resolution. Sci Data 5:180214. https://doi.org/10.1038/sdata.2018.214 Article  PubMed  PubMed Central  Google Scholar  * Benedict PK (1972) Sino-Tibetan: a conspectus. Cambridge

University Press, New York Book  Google Scholar  * Benedict PK (1976) Rhyming dictionary of written Burmese. Linguist Tibeto-Burman Area 3(1):1–93 Google Scholar  * Boas F (1911)

Introduction. In: Handbook of American Indian languages, Vol 1. Government Print Office (Smithsonian Institution, Bureau of American Ethnology, Bulletin 40), pp, 1–83 * Du Bois JA (1985)

Competing motivations. In: Haiman J (ed.) Iconicity in syntax. John Benjamins Publishing Company, Amsterdam, pp. 343–366 Chapter  Google Scholar  * Bradley D (1979) Proto-Loloish. Curzon

Press, London and Malmö Google Scholar  * Burenhult N, Levinson SC (2008) Language and landscape: a cross-linguistic perspective. Lang Sci 30(2–3):135–150.

https://doi.org/10.1016/j.langsci.2006.12.028 Article  Google Scholar  * Burling R (1983) The Sal languages. Linguist Tibeto-Burman Area 7(2):1–32 Google Scholar  * Burling R (2003) The

language of the Modhupur Mandi (Garo) Vol. III: glossary. University of Michigan, Ann Arbor * De Busser R (2015) The influence of social, cultural, and natural factors on language structure:

an overview. In: De Busser R, LaPolla RJ (eds) Cognitive linguistic studies in cultural contexts. John Benjamins Publishing Company, Amsterdam, pp. 1–28 Google Scholar  * Carling G (2017)

Diachronic atlas of comparative linguistics online. https://diacl.ht.lu.se/. Accessed 12 May 2022 * CASS (or Chinese Academy of Social Sciences) (1991) Zangmianyu yuyin he cihui

(Tibeto-Burman phonology and lexicon). China Social Sciences Press, Beijing * Chang H (1986) Lahuyu jianzhi (A concise grammar of Lahu). The Ethnic Publishing House, Beijing Google Scholar 

* Chen X, Wang Z, Bao Y (2021) Cool island effects of urban remnant natural mountains for cooling communities: a case study of Guiyang, China. Sustain Cities Soc 71:102983.

https://doi.org/10.1016/j.scs.2021.102983 Article  Google Scholar  * Chou F (1972) Archaic Chinese and Sino-Tibetan. J Chin Stud Chin Univ Hong Kong 5(1):159–237 Google Scholar  * Coblin WS

(1986) A sinologist’s handlist of Sino-Tibetan lexical comparisons. Steyler Verlag, Nettetal Google Scholar  * Coupé C, Maddieson I (2016) Quelle adaptation acoustique pour les langues du

monde? In: Actes du 13ème congrès Français d'acoustique, Université du Maine, Le Mans (France), 11–15 April 2016 * Croft W (2003) Typology and universals. Cambridge University Press,

Cambridge, UK Google Scholar  * Dai QX, Cui ZC (1985) Achangyu jianzhi (A sketch of Achang). The Ethnic Publishing House, Beijing Google Scholar  * Day JA (1998) Fog and mist. In: Herschy RW

(ed) Encyclopedia of Hydrology and Lakes. Springer, Dordrecht Google Scholar  * Ding SZ (2014) A grammar of Prinmi: based on the central dialect of northwest Yunnan, China. Brill, Leiden

Book  Google Scholar  * Ding SQ (2022) Jishishan Bao’anyu (Jishishan dialect of Bonan). https://zhongguoyuyan.cn/point/65603. Accessed 23 Dec 2022 * Domrös M, Peng G (1988) The climate of

China. Springer, Berlin and Heidelberg Book  Google Scholar  * Dong S, Huang C-R, Ren H (2020) Towards a new typology of meteorological events: a study based on synchronic and diachronic

data. Lingua 247:102894 Article  Google Scholar  * Dong S, Yang Y, Ren H, Huang C-R (2021) Directionality of atmospheric water in Chinese: a lexical semantic study based on linguistic

ontology. SAGE Open 11:1 Article  Google Scholar  * Van Driem G (1993) A grammar of Dumi. Mouton de Gruyter, Berlin Book  Google Scholar  * Van Driem G (2007) The diversity of the

Tibeto-Burman language family and the linguistic ancestry of Chinese. Bull Chin Linguist 1(2):211–270 Article  Google Scholar  * Dryer MS (2008) Word order in Tibeto-Burman languages.

Linguist Tibeto-Burman Area 31(1):1–83 Google Scholar  * Dunn M, Greenhill S, Levinson S et al. (2011) Evolved structure of language shows lineage-specific trends in word-order universals.

Nature 473:79–82. https://doi.org/10.1038/nature09923 Article  ADS  CAS  PubMed  Google Scholar  * Ember CR, Ember M (2010) Climate, econiche, and sexuality: influences on sonority in

language. Am Anthropol 109:180–185 Article  Google Scholar  * Evans JP (1999) Introduction to Qiang phonology and lexicon: synchrony and diachrony. Dissertation. University of California,

Berkeley Google Scholar  * Everett C (2017) Languages in drier climates use fewer vowels. Front Psychol 8:1285. https://doi.org/10.3389/fpsyg.2017.01285 Article  PubMed  PubMed Central 

Google Scholar  * Everett C, Blasi DE, Roberts SG (2015) Climate, vocal folds, and tonal languages: connecting the physiological and geographic dots. Proc Natl Acad Sci USA 112(5):1322–1327.

https://doi.org/10.1073/pnas.1417413112 Article  ADS  CAS  PubMed  PubMed Central  Google Scholar  * Fenning T (2014) Challenges and opportunities for the world’s forests in the 21st

century. Springer, Dordrech Book  Google Scholar  * Finley S (2018) Cognitive and linguistic biases in morphology learning. Wiley Interdiscip Rev 9(5):e1467. https://doi.org/10.1002/wcs.1467

Article  Google Scholar  * Fought JG, Munroe RL, Fought CR, Good EM (2004) Sonority and climate in a world sample of languages. Cross-Cult Res 38:27–51.

https://doi.org/10.1177/1069397103259439 Article  Google Scholar  * François A (2008) Semantic maps and the typology of colexification: intertwining polysemous networks across languages. In:

Vanhove M (ed) From polysemy to semantic change: towards a typology of lexical semantic associations. John Benjamins Publishing, Amsterdam, pp. 163–215 Chapter  Google Scholar  * Gabelentz

G (1901) Die sprachwissenschaft: ihre aufgaben, methoden und bisherigen ergebnisse. Tauchnitz, Leipzig Google Scholar  * Galvin JFP (2016) An introduction to the meteorology and climate of

the tropics. John Wiley & Sons, Chichester Google Scholar  * Gao Y (2022) Sichuan Kangding Muyayu xibu fangyan. Western dialect of Muya in Kangding, Sichuan,

https://zhongguoyuyan.cn/point/60773 Accessed 23 Dec 2022 * Gehrig-Downie C, Marquardt J, Obregón A, Bendix J, Gradstein SR (2012) Diversity and vertical distribution of filmy ferns as a

tool for identifying the novel forest type “tropical lowland cloud forest”. Ecotropica 18(1):35–44 Google Scholar  * Genga WM (2019) Sichuan Daofu Ergongyu (A grammar of Ergong in Sichuan).

Commercial Press, Beijing Google Scholar  * Glover WW (1972) A vocabulary of the Gurung language. Summer Institute of Linguistics and Institute of Nepal Studies, Tribhuvan University,

Kirtipur Google Scholar  * Gong QH (2007) Zhabayu yanjiu (A grammar of Zhaba). The Ethnic Publishing House, Beijing Google Scholar  * Gorenflo LJ, Romaine S, Mittermeier RA,

Walker-Painemilla K (2012) Co-occurrence of linguistic and biological diversity in biodiversity hotspots and high biodiversity wilderness areas. Proc Natl Acad Sci USA 109(21):8032–8037

Article  ADS  CAS  PubMed  PubMed Central  Google Scholar  * Gradstein SR, Obregon A, Gehrig C, Bendix J (2010) Tropical lowland cloud forest: A neglected forest type. In: Bruijnzeel LA,

Scatena FN, Hamilton LS (eds) Tropical montane cloud forests: science for conservation and management. Cambridge University Press, Cambridge, pp. 130–133 Google Scholar  * Greenhill S, Gray

R (2015) Bantu Basic Vocabulary Database. https://clics.clld.org/languages/bantubvd-2. Accessed 5 Jan 2023 * Haiman J (2010) Competing motivations. In: Song JJ (ed.) The Oxford handbook of

linguistic typology. Oxford University Press, Oxford, pp. 148–165 Google Scholar  * Hale A (1973) Clause, sentence, and discourse patterns in selected languages of Nepal IV: word lists.

Summer Institute of Linguistics and Tribhuvan University Press, Kathmandu Google Scholar  * Hammarström H, Forkel R, Haspelmath M, Bank S (2022) Glottolog 4.6. Max Planck Institute for

Evolutionary Anthropology, Leipzig Google Scholar  * Haspelmath M, Tadmor U (2009) World loanword database. Max Planck Institute for Evolutionary Anthropology, Leipzig Google Scholar  * He

JR, Jiang ZY (1985) Naxiyu jianzhi (A concise grammar of Naxi). The Ethnic Publishing House, Beijing Google Scholar  * Honkasalo S (2019) A grammar of eastern Geshiza: a culturally anchored

description. Dissertation, University of Helsinki * Hoshi M (1984) A Prakaa vocabulary: a dialect of the Manang language. Anthropological and linguistic studies of the Gandaki Area in Nepal

II. ILCAA, Tokyo * Huang BF (1992) Zangmianyuzu yuyan cihui (A Tibeto-Burman lexicon). Central Institute of Minorities, Beijing Google Scholar  * Huang C-R, Dong S, Yang Y, Ren H (2021) From

language to meteorology: kinesis in weather events and weather verbs across Sinitic languages. Humanit Soc Sci Commun 8:4 Article  Google Scholar  * Huang Y (2020) Zhabayu de mingwuhua he

guanxihua (Nominalization and relativization in nDrapa). Minzu Yuwen (Minority languages of China) 4:29–42 CAS  Google Scholar  * Jacques G (2015) On the cluster *sr– in Sino-Tibetan. J Chin

Linguist 43(1):215–223 Article  Google Scholar  * Jacques G (2021) A grammar of Japhug. Language Science Press, Berlin Google Scholar  * Jacques G, Michaud A (2011) Approaching the

historical phonology of three highly eroded Sino-Tibetan languages: Naxi, Na and Laze. Diachronica 28:468–498 Article  Google Scholar  * Jacques G (forthcoming) An overview of morphology in

Sino-Tibetan/Trans-Himalayan. In: Arkadiev P, Rainer F (eds) The Oxford handbook of historical morphology. Oxford University Press, Oxford * Jacquesson F (2008) A Kokborok grammar (Agartala

dialect). Kókborok Tei Hukumu Mission, Agartala Google Scholar  * Jaswal AK, Kore PA, Singh V (2017) Variability and trends in low cloud cover over India during 1961-2010. MAUSAM

68(2):235–252 Article  Google Scholar  * Jiang Y (2015) Dayang pumiyu cankao yufa (A grammar of Dayang Prinmi). China Social Sciences Press, Beijing Google Scholar  * Kaiping GA, Edwards O,

Klamer M (2019) LexiRumah 3.0.0. https://lexirumah.model-ling.eu/. Accessed 12 May 2022 * Kattel DB, Yao T, Yang K, Tian L, Yang G, Joswiak D (2013) Temperature lapse rate in complex

mountain terrain on the southern slope of the central Himalayas. Theor Appl Climatol 113:671–682 Article  ADS  Google Scholar  * Key MR, Comrie B (2015) The intercontinental dictionary

series. Max Planck Institute for Evolutionary Anthropology, Leipzig Google Scholar  * Konnerth L (2016) The Proto-Tibeto-Burman *gV-nominalizing prefix. Linguistics of the Tibeto-Burman Area

39(1):3–32 Article  Google Scholar  * Kurosaki Y, Kimura F (2002) Relationship between topography and daytime cloud activity around Tibetan Plateau. J Meteoroll Soc Jpn 80(6):1339–1355

Article  Google Scholar  * Lai YF (2017) Grammaire du khroskyabs de Wobzi. Dissertation, Université Sorbonne Paris Cité * LaPolla RJ (1987) Dulong and Proto-Tibeto-Burman. Linguist

Tibeto-Burman Area 10(1):1–43 Google Scholar  * LaPolla RJ, Huang CL (2003) A grammar of Qiang: with annotated texts and glossary. De Gruyter, Mouton, Berlin, New York Book  Google Scholar 

* Levinson SC (2003) Space in language and cognition: explorations in cognitive diversity. Cambridge University Press, Cambridge Book  Google Scholar  * Levinson SC, Wilkins DP (2006)

Grammars of space: explorations in cognitive diversity. Cambridge University Press, Cambridge Book  Google Scholar  * Li FW (1997) Xiahan zidian (Tangut-Chinese Dictionary). China Social

Sciences Press, Beijng Google Scholar  * Li C (2022a) Yunnan Ninglang Lisuyu Ninglang fangyan cuiyuhua (Cuiyu dialect of Ninglang Lisu in Yunnan). https://zhongguoyuyan.cn/point/60M40.

Accessed 23 Dec 2022 * Li C (2022b) Sichuan Dechang Lisuyu Nujiang fangyan Dechanghua (Dechang Dialect of Lisu). https://zhongguoyuyan.cn/point/60826. Accessed 23 Dec 2022 * Li C (2022c)

Yunnan Yongsheng Lisuyu Nujiang fangyan Liudetuyu (Yongsheng dialect of Lisu). https://zhongguoyuyan.cn/point/60717. Accessed 23 Dec 2022 * Liu CH (1995) Liuzhou fanyan cidian (A dictionary

of Liuzhou Mandarin). Jiangsu Education Press, Nanjing Google Scholar  * Liu GK (1998) Mawo Qiangyu yanjiu (A grammar of Mawo Qiang). Sichuan Ethnic Publishing House, Chengdu Google Scholar

  * Liu L (1984) Jingpozu yuyan jianzhi (A concise grammar of the Jingpho language). The Ethnic Publishing House, Beijing Google Scholar  * Liu YM, Yan YF, Lü JH, Liu XL (2018) Review of

current investigations of cloud, radiation and rainfall over the Tibetan Plateau with the CloudSat/CALIPSO dataset. Chin J Atmos Sci (in Chinese) 42(4):847–858.

https://doi.org/10.3878/j.issn.1006-9895.1805.17281 Article  Google Scholar  * Liu ZF (2022) (2022) Sichuan Yanbian Naxiyu dongbu fanyan Mosuohua. Mosuo speech in Yanbian, Sichuan,

https://zhongguoyuyan.cn/point/60M18 Accessed 23 Dec 2022 * Lu SZ (1983) Pumiyu jianzhi (A concise grammar of Prinmi). The Ethnic Publishing House, Beijing Google Scholar  * Lu SZ (2001)

Pumiyu fangyan yanjiu (A study of Prinmi dialects). The Ethnic Publishing House, Beijing Google Scholar  * Maddieson I (2018) Language adapts to environment: sonority and temperature. Front

Commun 3:28 Article  Google Scholar  * Maddieson I, Coupé C (2015) Human spoken language diversity and the acoustic adaptation hypothesis. J Acoust Soc Am 138(3):1838–1838.

https://doi.org/10.1121/1.4933848 Article  ADS  Google Scholar  * Maddieson I (2012) On the origin and distribution of complexity in phonological structure. In: Proceedings of the joint

conference JEP-TALN-RECITAL 2012. p7. Available online at: http://aclweb.org/anthology/F/F12/F12-4004.pdf * Marrison GE (1967) The classification of the Naga languages of north-east India

(Volume 2). Dissertation, University of London * Martin L (1986) Eskimo words for snow: a case study in the genesis and decay of an anthropological example. Am Anthropol 88:418–423 Article 

Google Scholar  * Matisoff JA (1990) On megalocomparison. Language 66(1):106–120 Article  Google Scholar  * Matisoff JA (1991) The mother of all morphemes: augmentatives and diminutives in

areal and universal perspective. In: Ratliff M, Schiller E (eds.). Papers from the First Annual Meeting of the Southeast Asian Linguistic Society. Arizona State University, Tempe Google

Scholar  * Matisoff JA (2003) Handbook of Proto-Tibeto-Burman: system and philosophy of Sino-Tibetan reconstruction. University of California Press, Berkeley Google Scholar  * Matisoff JA

(2006) English-Lahu lexicon. University of California Press, Berkeley Google Scholar  * Michaud A, Jacques G, Rankin RL (2012) Historical transfer of nasality between consonantal onset and

vowel: from C to V or from V to C? Diachronica 29(2):201–230 Article  Google Scholar  * Michaud A (2018) Na (Mosuo)-English-Chinese dictionary.

https://halshs.archives-ouvertes.fr/halshs-01204638v3/document. Accessed 22 Sept 2020 * Mortensen DR (2012) Database of Tangkhulic languages. http://stedt.berkeley.edu/search/. Accessed 9

Dec 2022 * Mu YZ, Sun HK (2012) Lisuyu fangyan yanjiu (A study of Lisu dialects). The Ethnic Publishing House, Beijing Google Scholar  * Muellner-Riehl AN (2019) Mountains as evolutionary

arenas: patterns, emerging approaches, paradigm shifts, and their implications for plant phylogeographic research in the Tibeto-Himalayan region. Front Plant Sci 10:195.

https://doi.org/10.3389/fpls.2019.00195 Article  PubMed  PubMed Central  Google Scholar  * Munroe RL, Silander M (1999) Climate and the consonant-vowel (CV) syllable: replication within

language families. Cross-Cult Res 33:43–62. https://doi.org/10.1177/106939719903300104 Article  Google Scholar  * Munroe RL, Munroe RH, Winters S (1996) Cross-cultural correlates of the

consonant-vowel syllable. Cross-Cult Res 30:60–83. https://doi.org/10.1177/106939719603000103 Article  Google Scholar  * Munroe RL, Fought JG, Macaulay RKS (2009) Warm climates and sonority

classes: not simply more vowels and fewer consonants. Cross-Cult Res 43:123–133. https://doi.org/10.1177/1069397109331485 Article  Google Scholar  * Nagano Y (1984) A Manang glossary.

Anthropological and linguistic studies of the Gandaki Area in Nepal II. ILCAA, Tokyo Google Scholar  * Nagano Y (2017) Cogtse rGyarong. In: Thurgood G, LaPolla RJ (eds) The Sino-Tibetan

languages. Routledge, London Google Scholar  * Nagano Y, Prins M (2013) rGyalrongic languages database. https://htq.minpaku.ac.jp/databases/rGyalrong/. Accessed 20 May 2022 * Nagaraja KS,

Sidwell P, Greenhill S (2013) A lexicostatistical study of the Khasian languages. Mon-Khmer Studies 42:1–11 Google Scholar  * Nichols J (1992) Linguistic diversity in space and time.

University of Chicago Press, Chicago Book  Google Scholar  * Nogués-Bravo D, Araújo MB, Romdal T, Rahbek C (2008) Scale effects and human impact on the elevational species richness

gradients. Nature 453(7192):216–219. https://doi.org/10.1038/nature06812 Article  ADS  CAS  PubMed  Google Scholar  * O’Meara C, Pérez Báez G (2011) Spatial frames of reference in

Mesoamerican languages. Lang Sci 33(6):837–852. https://doi.org/10.1016/j.langsci.2011.06.013 Article  Google Scholar  * Obregon A, Gehrig-Downie C, Gradstein SR, Bendix J (2014) The

potential distribution of tropical lowland cloud forest as revealed by a novel MODIS-based fog/low stratus night-time detection scheme. Remote Sens Environ 155:312–324.

https://doi.org/10.1016/j.rse.2014.09.005 Article  ADS  Google Scholar  * Obregon A, Gehrig-Downie C, Gradstein SR, Rollenbeck R, Bendix J (2011) Canopy level fog occurrence in a tropical

lowland forest of French Guiana as a prerequisite for high epiphyte diversity. Agric Forest Meteorol 151(3):290–300. https://doi.org/10.1016/j.agrformet.2010.11.003 Article  ADS  Google

Scholar  * Ouyang JY (1985) Luobazu yuyan jianzhi (A concise grammar of Bokar). The Ethnic Publishing House, Beijing Google Scholar  * Palmer B (2015) Topography in language: absolute frame

of reference and the topographic correspondence hypothesis. In: De Busser R, LaPolla RJ (eds) Cognitive linguistic studies in cultural contexts. John Benjamins Publishing Company, Amsterdam,

pp. 177–226 Google Scholar  * Pöhlker C, Wiedemann KT, Sinha B et al. (2012) Biogenic potassium salt particles as seeds for secondary organic aerosol in the Amazon. Science

337(6098):1075–8. https://doi.org/10.1126/science.1223264 Article  ADS  CAS  PubMed  Google Scholar  * Popovich HA, Popovich FB (2005) Maxakalí-English dictionary. Summer Institute of

Lingusitics, Cuiabá Google Scholar  * Prins M (2016) A grammar of rGyalrong, Jiaomuzu (kyom-kyo) dialects: a web of relations. Brill, Leiden Book  Google Scholar  * Pullum G (1991) The great

Eskimo vocabulary hoax and other irreverent essays on the study of language. University of Chicago Press, Chicago and London Google Scholar  * Qumu, TX (2022) Sichuan Mianning Yiyu beibu

fanyan Shuitianhua (Shuitian dialect of Liangshan Yi). https://zhongguoyuyan.cn/point/60832. Accessed 23 Dec 2022 * Regier T, Kemp C, Kay P (2015) Word meanings across languages support

efficient communication. In: MacWhinney B, O’Grady W (eds) The handbook of language emergence. Wiley-Blackwell, Hoboken, pp. 237–263 Chapter  Google Scholar  * Regier T, Carstensen A, Kemp C

(2016) Languages support efficient communication about the environment: words for snow revisited. PLoS ONE 11:e0151138 Article  PubMed  PubMed Central  Google Scholar  * Ring H (2015) A

grammar of Pnar. Dissertation, Nanyang Technological University * Rosch E (1999) Principles of categorization. In: Margolis E, Laurence S (eds.) Concepts: core readings. MIT Press,

Cambridge, MA, pp. 189–206 Google Scholar  * Rzymski C, Tresoldi T, Greenhill SJ et al. (2020) The database of cross-linguistic colexifications, reproducible analysis of cross-linguistic

polysemies. Sci Data 7(1):13. https://doi.org/10.1038/s41597-019-0341-x Article  PubMed  PubMed Central  Google Scholar  * Sagart L, Jacques G, Lai YF, Ryder R, Thouzeau V, Greenhill SJ,

List JM (2019) Dated language phylogenies shed light on the history of Sino-Tibetan. Proc Natl Acad Sci USA 116:10317–10322 Article  ADS  CAS  PubMed  PubMed Central  Google Scholar  * Sapir

E (1912) Language and environment. Am Anthropol 14:226–242 Article  Google Scholar  * Shi J (2009) Lianghe Achangyu cankao yufa (A grammar of Lianghe Achang). China Social Sciences Press,

Beijing Google Scholar  * Shi S (2018) Ethnic flows in the Tibetan-Yi corridor throughout history. Int J Anthropold Ethno 2:1–22 Google Scholar  * So-Hartmann H (1988) Notes on the Southern

Chin languages. Linguist Tibeto-Burman Area 11(2):98–119 Google Scholar  * Sun TS (2014) Typology of generic-person marking in Tshobdun Rgyalrong. In: Simmons RV, Van Auken NA (eds) Studies

in Chinese and Sino-Tibetan linguistics: dialect, phonology, transcription and text. Institute of Linguistics, Academia Sinica, Taipei Google Scholar  * Sun TS (1993) Tani synonym sets.

http://stedt.berkeley.edu/search/. Accessed 13 Jul 2022 * Tournadre N et al. (2009) Sherpa-English and English-Sherpa dictionary. Vajra Publications, Kathmandu Google Scholar  * Urban M

(2012) Analyzability and semantic associations in referring expressions: a study in comparative lexicology. Dissertation, Max Planck Institute for Evolutionary Anthropology, Leipzig Google

Scholar  * Urban M (2023) Foggy connections, cloudy frontiers: on the (non-)adaptation of lexical structures. Front Psychol 14:1115832 Article  PubMed  PubMed Central  Google Scholar  *

VanBik K (2009) Proto-Kuki-Chin: a reconstructed ancestor of the Kuki-Chin languages. STEDT, Berkeley Google Scholar  * Walcek CJ (1994) Cloud cover and its relationship to relative humidity

during a springtime midlatitude cyclone. Mon Weather Rev 122(6):1021–1035 Article  ADS  Google Scholar  * Wang P (1994) Guiyang fangyan cidian (Guiyang Mandarin lexicon). Jiangsu Education

Press, Jiangsu Google Scholar  * Wei J, Duan KQ, Xin R (2020) Cloud occurrence probability and its radiative forcing characteristics in Qinghai-Tibet Plateau. J Glaciol Geocryol

42(2):368–377 Google Scholar  * Weidert A (1987) Tibeto-Burman tonology: a comparative account. John Benjamins Publishing Company, Amsterdam and Philadelphia Book  Google Scholar  * Wen J

(2022) Yunnan Mangshi Zhongshan Langsuyu (Mangshi Zhongshan Dialect of Maru). https://zhongguoyuyan.cn/point/60855. Accessed 23 Dec 2022 * Witkowski SR, Brown CH (1985) Climate, clothing,

and body-part nomenclature. Ethnology 24:197–214 Article  Google Scholar  * Xu Y, Duong K, Malt BC, Jiang S, Srinivasan M (2020) Conceptual relations predict colexification across languages.

Cognition 201:104280–104280. https://doi.org/10.1016/j.cognition.2020.104280 Article  PubMed  Google Scholar  * Yan RX, Wong SW (1988) Pumizu jianshi (A sketch of the Prinmi nationality).

Yunnan People Publisher, Kunming Google Scholar  * Yang C (2010) Lalo regional varieties: phylogeny, dialectometry, and sociolinguistics. Dissertation, La Trobe University * Yang XX (2014)

Baiyu Baishihua cankao yufa (A reference grammar of Baishi Bai language). Dissertation, Xiamen University * Zhan BH, Chen XJ, Li R (1997) Dongguan fangyan cidian (A lexicon of Dongguan Yue).

Jiangsu Education Publishing House, Nanjing Google Scholar  * Zhang JC (1986) Cangluo Menbayu jianzhi (Brief description of the Cangluo Menba language). The Ethnic Publishing House, Beijing

Google Scholar  * Zhang MH, Yan S, Pan WY, Jin L (2019) Phylogenetic evidence for Sino-Tibetan origin in northern China in the Late Neolithic. Nature 569:112–115.

https://doi.org/10.1038/s41586-019-1153-z Article  ADS  CAS  PubMed  Google Scholar  * Zhang SY (2020) Le rgyalrong situ de Brag-bar et sa contribution à la typologie de l'expression

des relations spatiales: l'orientation et le mouvement associé. Dissertation, Institut National des Langues et Civilisations Orientales * Zhao QL (2022) Yunnan Lijiang Naxiyu xibu

fanyan Dayanhua (Dayan Naxi in Lijiang, Yunnan). https://zhongguoyuyan.cn/point/60852. Accessed 23 Dec 2022 * Zheng WX (2016) A grammar of Longxi Qiang. Dissertation, National University of

Singapore * Zhou MC (2004) Maqu zangyu yanjiu (Grammar of Maqu Tibetan). The Ethnic Publishing House, Beijing Google Scholar  * Zhou CF (2019) Re’ela Qiangyu cankao yufa (A grammar of Re’ela

Qiang). Dissertation, Shanghai Normal University Download references ACKNOWLEDGEMENTS For valuable feedback on the linguistic data of this work, we thank Dr. Cathryn Yang, Dr. Sizhi Ding,

Dr. Yang Huang, and Dr. Yunfan Lai. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * The Education University of Hong Kong, Hong Kong, People’s Republic of China Hongdi Ding * Harbin Institute

of Technology, Shenzhen, People’s Republic of China Sicong Dong Authors * Hongdi Ding View author publications You can also search for this author inPubMed Google Scholar * Sicong Dong View

author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS HDD: conception and design of study; data collection, analysis and interpretation; drafting the

manuscript, revising the manuscript critically for important intellectual content; approval of the version of the manuscript to be submitted; agreement to be accountable for all aspects of

the work. SCD: conception and design of study; data collection, analysis and interpretation; drafting the manuscript, revising the manuscript critically for important intellectual content;

approval of the version of the manuscript to be submitted; agreement to be accountable for all aspects of the work. CORRESPONDING AUTHORS Correspondence to Hongdi Ding or Sicong Dong. ETHICS

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