Chinese and its mountain neighbors
Sino-Tibetan is the second-largest language family by native speakers, with around 1.3 billion speakers concentrated in China, Tibet, and the Himalayan regions. The Sinitic branch includes Mandarin, Cantonese, Wu, Min, and other regional languages often called 'dialects' of Chinese, but which are mutually unintelligible and function as separate languages linguistically. The Tibeto-Burman branch comprises Tibetan, Burmese, and hundreds of smaller languages spoken in the mountainous zones of Southeast Asia.
Despite the modern prominence of Mandarin, the actual branches of Sino-Tibetan are highly diverse. Mandarin is relatively simplified compared to other Sinitic languages, many of which preserve consonant clusters and final consonants lost in Mandarin. The relationship between Sinitic and Tibeto-Burman languages is ancient, and the exact mechanism of their divergence remains debated.
Tone and script as distinguishing features
Sino-Tibetan languages are famous for tone systems, where pitch contours distinguish word meanings. Mandarin has four tones; Cantonese has six or nine depending on analysis. Burmese also employs tones, though Tibetan languages typically do not. Written Chinese characters, used historically by Japanese, Korean, and Vietnamese, originated in the Sinitic branch and represent morphemes rather than phonemes. This writing system, older than alphabetic scripts in the region, shapes how written communication flows across language boundaries.