river vs Volga River

river and Volga River both are nouns.

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

river (noun)	Volga River (noun)
a large natural stream of water (larger than a creek)	a Russian river; the longest river in Europe; flows into the Caspian Sea