Potomac vs river

Potomac and river both are nouns.

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

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