Western Siouan languages
The Western Siouan languages, also called Siouan proper or simply Siouan, are a large language family native to North America. They are closely related to the Catawban languages, sometimes called Eastern Siouan, and together with them constitute the Siouan (Siouan–Catawban) language family.
Assiniboine language
Sioux, Assiniboine, and Stoney are closely related languages of the Dakota family. Many linguists consider Assiniboine and Stoney to be dialects. However, they are mutually unintelligible. Parks and DeMallie report that they are not variant forms of a single dialect, but that Assiniboine is closer to the Sioux dialects than it is to Stoney. The exact number of interrelationships among the subdialects and dialects comprising this continuum is unknown.