Danube River vs river

Danube River and river both are nouns.

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

Danube River (noun)	river (noun)
the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea	a large natural stream of water (larger than a creek)