Tsat (also known as Utsat, Utset, Huihui, Hui, or Hainan Cham) is a language spoken on Hainan Island in China. Tsat is a member of the Malayo-Polynesian group within the Austronesian language family, and is related to the Cham languages, originally from the coast of present-day Vietnam.
Unusually for a Malayo-Polynesian language, Tsat has developed into a solidly tonal language, probably as a result of areal linguistic effects and contact with Chinese, Hlai/Li, and the other tonal languages of Hainan.
It is part of the Austroasiatic language family, of which it has the most speakers by a significant margin (three to four times the number of speakers of Khmer, the second most spoken Austroasiatic language).
Vietnamese is generally said to be part of the Viet-Muong grouping of the Mon-Khmer branch of the Austroasiatic language family, a family that also includes Khmer, spoken in Cambodia, as well as various tribal and regional languages, such as the Munda languages, spoken in northeastern India, and others in southern China.
In fact, as the vernacular language of Vietnam gradually grew in prestige toward the beginning of the second millennium, the Vietnamese language was written using Chinese characters (see Chu Nom) adapted to write Vietnamese, in a similar pattern as used in Japan (see kanji), Korea and other countries in the Chinese cultural sphere.