river vs Ouachita River

river and Ouachita River both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Ouachita River	Yes	No	No	No

river (noun)	Ouachita River (noun)
a large natural stream of water (larger than a creek)	a river that rises in western Arkansas and flows southeast into eastern Louisiana to become a tributary of the Red River