Vietnamese was historically written in classical Chinese characters (汉字, until ~1900) and in 字喃 (Chữ Nôm, a Vietnamese-modified Chinese script). It now uses the Latin-based quốc ngữ alphabet, designed by Portuguese Jesuits in the 17th century.
usage
越南语 (Yuènányǔ) emphasizes the spoken language; 越南文 emphasizes the written language and literary tradition. Same 语 vs 文 contrast as 中文/汉语, 英文/英语.
