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.
Mandan
The Mandan language or "Nų́ų́ʔetaa íroo" belongs to the Siouan language family. It was initially thought to be closely related to the languages of the Hidatsa and the Crow. However, since the Mandan language has been in contact with Hidatsa and Crow for many years, the exact relationship between Mandan and other Siouan languages (including Hidatsa and Crow) has been obscured. For this reason, linguists classify Mandan most often as a separate branch of the Siouan family.