The varieties of Chinese are usually considered by native speakers to be regional variants of ethnic Chinese speech, without consideration of whether they are mutually intelligible. Due to their lack of mutual intelligibility, linguists generally describe them as distinct languages, perhaps hundreds, sometimes noting that they are more varied than the Romance languages.[b] Investigation of the historical relationships among the Sinitic languages is just getting started. Currently, most classifications posit 7 to 13 main regional groups, based on often superficial phonetic developments, of which the most populous by far is Mandarin (about 800 million speakers, e.g. Southwestern Mandarin), followed by Min (75 million, e.g. Southern Min), Wu (74 million, e.g. Shanghainese), Yue (68 million, e.g. Cantonese). These groups are unintelligible to each other, and generally many of their subgroups are mutually unintelligible as well (e.g., not only is Min Chinese a family of mutually unintelligible languages, but Southern Min itself is not a single language). There are, however, several transitional areas, where languages and dialects from different branches share enough features for some limited intelligibility between neighboring areas. Examples are New Xiang and Southwest Mandarin, Xuanzhou Wu and Lower Yangtze Mandarin, Jin and Central Plains Mandarin, and certain divergent dialects of Hakka with Gan (though these are unintelligible with mainstream Hakka). All varieties of Chinese are tonal to at least some degree and largely analytic.
Linguists classify all varieties of Chinese as part of the Sino-Tibetan language family, together with Burmese, Tibetan and many other languages spoken in the Himalayas and the Southeast Asian Massif. Although the relationship was first proposed in the early 19th century and is now broadly accepted, reconstruction of Sino-Tibetan is much less developed than that of families such as Indo-European or Austroasiatic. Difficulties have included the great diversity of the languages, the lack of inflection in many of them, and the effects of language contact. In addition, many of the smaller languages are spoken in mountainous areas that are difficult to reach, and are often also sensitive border zones. Without a secure reconstruction of proto-Sino-Tibetan, the higher-level structure of the family remains unclear. A top-level branching into Chinese and Tibeto-Burman languages is often assumed, but has not been convincingly demonstrated.