Vietnamese is the national language of Vietnam and is written today with the Latin-based chữ Quốc ngữ script.
Vietnamese belongs to the Vietic branch of the Austroasiatic language family. It has been strongly influenced by centuries of contact with Chinese, and much of its formal vocabulary contains Sino-Vietnamese elements.
Chữ Quốc ngữ was developed from the 17th century onward by Portuguese missionaries and other Catholic scholars, with major contributions from Alexandre de Rhodes. The script uses Latin letters together with additional marks for Vietnamese sounds and tones.
Chinese characters and the locally adapted chữ Nôm system were historically important in Vietnam. Chữ Quốc ngữ expanded during the 19th and early 20th centuries and became dominant in education, publishing, and administration. Modern Vietnamese is tonal, so diacritics can distinguish both vowel quality and lexical tone.