Siouan vs Indian language

Siouan and Indian language both are nouns.

Word	Noun	Adjective	Verb	Adverb
Siouan	Yes	Yes	No	No
Indian language	Yes	No	No	No

As nouns, Indian language is a hypernym of Siouan; that is, Indian language is a word with a broader meaning than Siouan:

Siouan (noun)	Indian language (noun)
a family of North American Indian languages spoken by the Sioux	any of the languages spoken by Amerindians
a member of a group of North American Indian peoples who spoke a Siouan language and who ranged from Lake Michigan to the Rocky Mountains

Siouan (adjective)	Indian language (adjective)
of or relating to the Sioux people or their language and culture