Siouan languages
Siouan or Siouan–Catawban is a language family of North America that is located primarily in the Great Plains, Ohio and Mississippi valleys and southeastern North America with a few other languages in the east.
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.