Arkansas River vs river

Arkansas River and river both are nouns.

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

Arkansas River (noun)	river (noun)
a river that rises in the Rocky Mountains in Colorado and flows southeast through Kansas and Oklahoma and through Arkansas to become a tributary of the Mississippi River	a large natural stream of water (larger than a creek)