river vs Danube

river and Danube both are nouns.

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

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