Potomac River vs river

Potomac River and river both are nouns.

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

Potomac River (noun)	river (noun)
a river in the east central United States; rises in West Virginia in the Appalachian Mountains and flows eastward, forming the boundary between Maryland and Virginia, to the Chesapeake Bay	a large natural stream of water (larger than a creek)