Pittsburgh vs metropolis

Pittsburgh and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pittsburgh	Yes	No	No	No
metropolis	Yes	No	No	No

Pittsburgh (noun)	metropolis (noun)
a city in southwestern Pennsylvania where the confluence of the Allegheny River and Monongahela River forms the Ohio River; long an important urban industrial area; site of Carnegie Mellon University and the University of Pittsburgh	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts