The Dai people form one of the 56 ethnic groups officially recognized by the People's Republic of China, and are closely related to the Lao and Thai people who form a majority in Laos and Thailand. Originally, the Tai, or Dai, lived closely together in modern Yunnan Province until political chaos and wars in the north at the end of the Tang and Song Dynasty and various nomadic peoples prompted some to move further south into modern Laos then Thailand. As with many other officially recognized ethnic groups in China (See Gaoshan and Yao), the term Dai at least within Chinese usage is an umbrella term and as such has no equivalent in Tai languages who have only more general terms for 'Tai peoples in general' (e.g., Tai Lue: tai˥˩, but this term refers to all Dai people, not including Zhuang) and 'Tai people in China' (e.g., Thai: ชาวไทในจีน'), both of which include the Zhuang for example which is not the case in the Chinese; and more specific terms, as shown in the table below. Therefore the word Dai, like with the aforementioned Yao, is a Han-Chinese cultural concept which has now been adopted by other languages such as English, French and German (see respective Wikipedias). As a solution in the Thai language, however, as in English, the term Tai Lue can be used to mean Dai, despite referring to other groups as in the table below. This is because the two main groups actually bear the same name, both meaning 'Northern Tai' (lue and nüa are cognate).
Although they are officially recognized as a single people by the Chinese state, these Tai people form several distinct cultural and linguistic groups. The two main languages of the Dai are Dai Lü (Sibsongbanna Dai) and Dai Nüa (Daihong Dai); two other written languages used by the Dai are
Tày Pong and Tai Dam. They all are Tai languages, a group of related languages that includes Thai, Lao, and Zhuang, and part of the Tai–Kadai language family. Various dialects of the Tai/Dai language family are spoken from Assam, India to Taiwan and Shanxi Province, China. The Dai people follow their traditional religion as well as Theravada Buddhism, and maintain similar customs and festivals (such as Songkran) to the other Tai-speaking peoples and more broadly, in regards to some cultural aspects, to the unrelated dominant ethnic groups of Myanmar, Cambodia and Sri Lanka. They are among the few natives groups in China who nominally practice the Theravada school of Buddhism.