Rostov na Donu vs Rostov

Rostov na Donu and Rostov both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rostov na Donu	Yes	No	No	No
Rostov	Yes	No	No	No

As nouns, Rostov na Donu and Rostov are synonyms defined as:

Rostov na Donu and Rostov: a seaport on the Don River near the Sea of Azov in the European part of Russia

Other synonyms of Rostov na Donu include Rostov-on-Don, Rostov on Don.

Rostov na Donu (noun)	Rostov (noun)
a seaport on the Don River near the Sea of Azov in the European part of Russia	a seaport on the Don River near the Sea of Azov in the European part of Russia