Chinese, also known as Sinitic, is a branch of the Sino-Tibetan language family consisting of hundreds of local varieties, many of which are not mutually intelligible. The differences are greater than within the Romance languages, with variation particularly strong in the more mountainous southeast of mainland China. The varieties are typically classified into several groups: Mandarin, Wu, Min, Xiang, Gan, Hakka and Yue, though some varieties remain unclassified. These groups are neither clades nor individual languages defined by mutual intelligibility, but reflect common phonological developments from Middle Chinese.