the various Khmu settlements became isolated, surrounded and partially influenced by the dominant groups of their respective areas. Accordingly, the Khmu now recognize subdivisions among themselves which are differentiated primarily by dialect. These subgroups are called tmowy () in Khmu. Some of the larger tmowy are the Tmowy Mea [tmɔi mɛ], Tmowy Ksak [tmɔi ksăk], Tmowy Rok [tmɔi rɔk] (Lao: kha hok). The Khmu north of the Tha River (nam tha), who often live in close contact with the lowland Tai Lü and Thai Yuan peoples, distinguish groups including the Tmowy Lü [tmɔi lɯʔ], Tmowy Yuan and Tmowy Khuen (Khuen is often a synonym for "Khmu" in general). Aside from their geographical separation, the subgroups' primary differences are in dialect. However, there are slight variations in customs and cultural practices among the various tmowy. The Khmu refer to others within their own tmowy as tay-haem ("older siblings-younger siblings"), expressing solidarity and shared ritual/common ancestral worship while referring to other Khmu by the name of their respective groups. The Khmu groups north of the Tha River in particular, whose names reflect their partial identification with the Buddhist Tai cultures, have acculturated to the dominant ethnic groups of the region. They are often contrasted with the Khmu Roek who live higher up in the hills and retain some older customs that other groups have abandoned. While the Khmu Roek are often respected as the center of the Khmu "socio-economic ritual complex", "Roek" is also used by more assimilated Khmu as an appellation for "backwood" Khmu regardless of their tmowy. Language The Khmu language belongs to the Austro-Asiatic language family, in which several closely related languages including Puoc, O’du and Kniang, among others, are grouped together forming the Khmuic branch. The many dialects of Khmu differ primarily in consonant inventory, existence of register, and the degree to which the language has been influenced by the surrounding national language(s). Dialects are, for the most part, mutually intelligible; however communication can be difficult between speakers of geographically distant dialects. The dialects of Khmu can be broadly categorized into two groups, Western Khmu and Eastern Khmu. Western Khmu dialects have fewer consonant phonemes and instead use phonemic register contrast of "lax" breathy register and "tense" modal register. In at least one dialect of Western Khmu, Khmu Roek, tonogenesis is evident as the register contrast has developed into a system of two phonemic tones with six phonetic