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. Variation is particularly strong in the more mountainous southeast part 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.
Chinese varieties differ most in their phonology, and to a lesser extent in vocabulary and syntax. Southern varieties tend to have fewer initial consonants than northern and central varieties, but more often preserve the Middle Chinese final consonants. All have phonemic tones, with northern varieties tending to have fewer distinctions than southern ones. Many have tone sandhi, with the most complex patterns in the coastal area from Zhejiang to eastern Guangdong.
Standard Chinese, a form of Mandarin, takes its phonology from the Beijing dialect, with vocabulary from the Mandarin group and grammar based on literature in the modern written vernacular. It is one of the official languages of China.
Taiwanese Mandarin is one of the official languages of Taiwan. Standard Singaporean Mandarin is one of the four official languages of Singapore. Chinese (specifically, Mandarin Chinese) is one of the six official languages of the United Nations.
At the end of the 2nd millennium BC, a form of Chinese was spoken in a compact area around the lower Wei River and middle Yellow River. From there it expanded eastwards across the North China Plain to Shandong and then south into the valley of the Yangtze River and beyond to the hills of south China. As the language spread, it replaced formerly dominant languages in those areas, and regional differences grew. Simultaneously, especially in periods of political unity, there was a tendency to promote a central standard to facilitate communication between people from different regions.