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 non-Tibeto-Burman varieties), has its historical reason, namely the relics of Proto-Tibeto-Burman. However, other than the phylogenetic factors, an underlying reason can be attributed to the environmental influence. The present findings indicate that fog-cloud similarity is more likely to happen at higher elevations, particularly between the range of 1000 m to 3000 m above sea 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.

从词汇上看，根据我们的 234 个藏缅语变体数据库，52.99% 的藏缅语（汉藏语系的非汉语支）将雾视为与云相同或相似的事物；这种雾云相似性在藏缅语中存在三种词汇关系，即“云”与“雾”共词、“云”是“雾”的上位词、“云”是“雾”的构成词。其余藏缅语使用语义上不连贯的词来描述雾和云。与跨喜马拉雅地区使用的非藏缅语相比，藏缅语的雾云相似度比例较高（即 10.80%，这是基于我们数据库中 213 个非藏缅语的结果）缅族品种），有其历史原因，即原藏缅语的遗迹。然而，除了系统发育因素外，一个根本原因可以归因于环境影响。目前的研究结果表明，雾云相似性更有可能发生在较高海拔地区，特别是在海拔 1000 米至 3000 米的范围内。回顾气象特征发现，藏缅地区由于山地环境，具有高湿度、通过地形隆升等低云形成的理想条件。由于说藏缅语的人生活在高海拔地区，因此该地区的主要云层——低云——可能会包围他们或在他们的视线之下。因此，他们可能会发现很难或没有必要区分雾和低云。我们的结论也得到了其他语系和地区语言的支持，例如高加索地区的达吉斯坦语言和安第斯山脉中部的语言。此外，目前的研究结果与有效沟通的理论相一致。也就是说，表现出雾云相似性的语言适应更高的海拔，而较少需要通过使用完全不同且不相关的语言形式来区分这两个概念；相反，表现出雾云分歧的语言更需要这样做，这也是它们对语言外环境的适应所致。最后，热带气候是雾-云相似性的另一个可能的预测因子，被确定为未来的研究方向。显示出雾云相似性的语言适应较高的海拔，较少需要通过使用完全不同且不相关的语言形式来区分这两个概念；相反，表现出雾云分歧的语言更需要这样做，这也是它们对语言外环境的适应所致。最后，热带气候是雾-云相似性的另一个可能的预测因子，被确定为未来的研究方向。显示出雾云相似性的语言适应较高的海拔，较少需要通过使用完全不同且不相关的语言形式来区分这两个概念；相反，表现出雾云分歧的语言更需要这样做，这也是它们对语言外环境的适应所致。最后，热带气候是雾-云相似性的另一个可能的预测因子，被确定为未来的研究方向。