Siouan languages
Authors who call the entire family "Siouan" distinguish the two branches as "Western Siouan" and "Eastern Siouan" or as "Siouan-proper" and "Catawban". Others restrict the name "Siouan" to the western branch and use the name "Siouan–Catawban" for the entire family. Generally, however, the name "Siouan" is used without distinction.
Yuchi language
Yuchi is classified as a language isolate, because it is not known to be related to any other language. Various linguists have made claims, however, that the language has a distant relationship with the Siouan family: Sapir in 1921 and 1929, Haas in 1951, and 1964, Elmendorf in 1964, Rudus in 1974, and Crawford in 1979.