medical center vs metropolis

medical center and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
medical center	Yes	No	No	No
metropolis	Yes	No	No	No

medical center (noun)	metropolis (noun)
the part of a city where medical facilities are centered	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts