Danube River vs Danau

Danube River and Danau both are nouns.

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

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

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

Other synonyms of Danube River include Danube.

Danube River (noun)	Danau (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