Yellowstone River vs river

Yellowstone River and river both are nouns.

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

Yellowstone River (noun)	river (noun)
a tributary of the Missouri River that flows through the Yellowstone National Park	a large natural stream of water (larger than a creek)