Danube River vs Danube

Danube River and Danube both are nouns.

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

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

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

Other synonyms of Danube River include Danau.

Danube River (noun)	Danube (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