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.
Middle Chinese was the language used during Northern and Southern dynasties and the Sui, Tang, and Song dynasties (6th through 10th centuries CE).
In addition, many of the smaller languages are spoken in mountainous areas that are difficult to reach, and are often also sensitive border zones.
Scholars have attempted to reconstruct the phonology of Old Chinese by comparing later varieties of Chinese with the rhyming practice of the Classic of Poetry and the phonetic elements found in the majority of Chinese characters.
Most of these groups are mutually unintelligible, although some, for example like Xiang and certain Southwest Mandarin dialects, may share common terms and some degree of intelligibility. Standard Chinese (Pǔtōnghuà/Guóyǔ/Huáyǔ) is a standardized form of spoken Chinese based on the Beijing dialect of Mandarin.
It is the official language of China and Taiwan, as well as one of the four official languages of Singapore.