Chinese ( 中国的 ) is a group of related language varieties, several of which are not mutually intelligible, and is variously described as a language or language family. It is the official language of the People's Republic of China and Taiwan, as well as one of four official languages of Singapore. It is one of the six official languages of the United Nations. Chinese forms one of the branches of the Sino-Tibetan language family. About one-fifth of the world's population, or over one billion people, speaks some form of Chinese as their native language. Chinese is often described as a "monosyllabic" language. However, this is only partially correct. It is largely accurate when describing Classical Chinese and Middle Chinese; in Classical Chinese, for example, perhaps 90% of words correspond to a single syllable and a single character.