Caspian vs Caspian Sea

Caspian and Caspian Sea both are nouns.

Word	Noun	Adjective	Verb	Adverb
Caspian	Yes	No	No	No
Caspian Sea	Yes	No	No	No

As nouns, Caspian and Caspian Sea are synonyms defined as:

Caspian and Caspian Sea: a large saltwater lake between Iran and Russia fed by the Volga River; the largest inland body of water in the world

Caspian (noun)	Caspian Sea (noun)
a large saltwater lake between Iran and Russia fed by the Volga River; the largest inland body of water in the world	a large saltwater lake between Iran and Russia fed by the Volga River; the largest inland body of water in the world