Penobscot River vs river

Penobscot River and river both are nouns.

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

Penobscot River (noun)	river (noun)
a river in central Maine flowing into Penobscot Bay	a large natural stream of water (larger than a creek)