Danube vs Danube River

Danube and Danube River both are nouns.

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

As nouns, Danube and Danube River are synonyms defined as:

Danube and Danube River: the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea

Other synonyms of Danube include Danau.

Danube (noun)	Danube River (noun)
the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea	the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea