Linguists have identified these sounds by comparing the categories with pronunciations in modern varieties of Chinese, borrowed Chinese words in Japanese, Vietnamese, and Korean, and transcription evidence.The resulting system is very complex, with a large number of consonants and vowels, but they are probably not all distinguished in any single dialect.Most linguists now believe it represents a diasystem encompassing 6th-century northern and southern standards for reading the classics.
Chinese is spoken by the Han majority and many minority ethnic groups in China.
The phonetic categories of Archaic Chinese can be reconstructed from the rhymes of ancient poetry.
During the Northern and Southern dynasties period, Middle Chinese went through several sound changes and split into several varieties following prolonged geographic and political separation.
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.