Danube vs river

Danube and river both are nouns.

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

Danube (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)