The Bunu (Punu) are the Yao people who speak Hmongic languages. That is, Bunu in the broad sense is a cultural rather than linguistic group. Strecker (1987) had classified Bunu proper (Bu-Nao) as a Western (Chuanqiandian) Hmongic language, and the other Bunu (or Punuic) languages—Younuo, Wunai (Hm Nai), and Jiongnai (Kiong Nai)—as distinct branches of Hmongic. Matisoff (2001) grouped all of these together in a Bunu branch of Hmongic (that is, outside Western Hmongic). Ratliff (2010) returned Bunu proper (Bu-Nao) to Western Hmongic, and moved Jiongnai to its own peripheral branch of Hmongic, but did not address Younuo or Wunai. Mao Zongwu (1997) found that Younuo, Wunai, and Pa-Hng form a distinct branch of Hmongic.
The Bunu languages form a group in Chinese classification, but that is because Chinese classifications are not purely linguistic, but take into account ethnic identity.