En (autonym: aiɲ˥˧; also known as Nùng Vên) is a Kra language spoken in Vietnam. Before its discovery in 1998, En language was undistinguished from Nùng, which is a Central Tai language closely related to Zhuang. In the late 1990s, Vietnamese linguist Hoàng Văn Ma had first recognized that it was not a Tai language, ultimately leading to field work distinguishing En as a separate language. Researchers have determined En to be one of the Buyang languages.