Saint Johns River vs river

Saint Johns River and river both are nouns.

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

Saint Johns River (noun)	river (noun)
a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean	a large natural stream of water (larger than a creek)