river vs Potomac

river and Potomac both are nouns.

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

river (noun)	Potomac (noun)
a large natural stream of water (larger than a creek)	term sometimes used to refer to Washington, D.C.
	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