Sioux is a Siouan language.
Sioux has 3 major regional varieties, with various sub-lects:
Yankton (a.k.a. Yankton-Yanktonai, Dakota) Lakota (a.k.a. Lakhota, Teton, Teton Sioux)
- Santee (a.k.a. Dakota)
- Northern Lakota
- Southern Lakota
Dakotan languages/varieties are often classified according to their reflexes of Proto-Siouan *R (some r-like sound, but distinct from Proto-Siouan *r). Santee and Yankton-Yanktonai are both d varieties (showing a reflex of d for *R, and thus pronouncing their autonym as dakhóta), while Lakota is a l variety (pronouncing their autonym Lakhóta).
- DeMallie, Raymond J. (2001). Sioux until 1850. In R. J. DeMallie (Ed.), Handbook of North American Indians: Plains (Vol. 13, Part 2, pp. 718-760). W. C. Sturtevant (Gen. Ed.). Washington, D.C.: Smithsonian Institution. ISBN 0-16-050400-7.
- Parks, Douglas R.; & Rankin, Robert L. (2001). The Siouan languages. In Handbook of North American Indians: Plains (Vol. 13, Part 1, pp. 94-114). Washington, D.C.: Smithsonian Institution.
- de Reuse, Willem J. (1987). One hundred years of Lakota linguistics (1887-1987). Kansas Working Papers in Linguistics, 12, 13-42. (Online version: https://kuscholarworks.ku.edu/dspace/handle/1808/509).
- de Reuse, Willem J. (1990). A supplementary bibliography of Lakota languages and linguistics (1887-1990). Kansas Working Papers in Linguistics, 15 (2), 146-165. (Studies in Native American languages 6). (Online version: https://kuscholarworks.ku.edu/dspace/handle/1808/441).
- Rood, David S.; & Taylor, Allan R. (1996). Sketch of Lakhota, a Siouan language. In Handbook of North American Indians: Languages (Vol. 17, pp. 440-482). Washington DC: Smithsonian Institution.