Siouan languages
Siouan languages can be grouped into the Western Siouan languages and Catawban languages. The Western Siouan languages can be divided into Missouri River languages (such as Crow and Hidatsa), Mandan, Mississippi River languages (such as Dakotan, Chiwere-Winnebago, and Dhegihan languages), and Ohio Valley Siouan branches. The Catawban languages consist only of Catawban and Woccon.
Sioux language
Sioux has three major regional varieties, with other sub-varieties:Yankton-Yanktonai (Western Dakota) stands between Santee-Sisseton (Eastern Dakota) and Lakota within the dialect continuum. It is phonetically closer to Santee-Sisseton but lexically and grammatically, it is much closer to Lakota. For this reason Lakota and Western Dakota are much more mutually intelligible than each is with Eastern Dakota. The assumed extent of mutual intelligibility is usually overestimated by speakers of the language. While Lakota and Yankton-Yanktonai speakers understand each other to a great extent, they each find it difficult to follow Santee-Sisseton speakers.