river vs Saint John River

river and Saint John River both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Saint John River	Yes	No	No	No

river (noun)	Saint John River (noun)
a large natural stream of water (larger than a creek)	a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy