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.
Copula (linguistics)
In Siouan languages like Lakota, in principle almost all words—according to their structure—are verbs. So not only (transitive, intransitive and so-called 'stative') verbs but even nouns often behave like verbs and do not need to have copulas.