chain of mountains vs Caucasus

chain of mountains and Caucasus both are nouns.

Word	Noun	Adjective	Verb	Adverb
chain of mountains	Yes	No	No	No
Caucasus	Yes	No	No	No

chain of mountains (noun)	Caucasus (noun)
a series of hills or mountains	a large region between the Black and Caspian seas that contains the Caucasus Mountains; oil is its major resource
	the mountain range in Caucasia between the Black Sea and the Caspian Sea that forms part of the traditional border between Europe and Asia