The varieties of Chinese are usually described by native speakers as dialects of a single Chinese language, but linguists note that they are as diverse as a language family.[b] The internal diversity of Chinese has been likened to that of the Romance languages, but may be even more varied. There are between 7 and 13 main regional groups of Chinese (depending on classification scheme), of which the most spoken by far is Mandarin (about 960 million, e.g. Southwestern Mandarin), followed by Wu (80 million, e.g. Shanghainese), Min (70 million, e.g. Southern Min), Yue (60 million, e.g. Cantonese), etc. Most of these groups are mutually unintelligible, and even dialect groups within Min Chinese may not be mutually intelligible. Some, however, like Xiang and certain Southwest Mandarin dialects, may share common terms and a certain degree of intelligibility. All varieties of Chinese are tonal and analytic.
Most 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.