metropolis vs Aachen

metropolis and Aachen both are nouns.

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

metropolis (noun)	Aachen (noun)
people living in a large densely populated municipality	a city in western Germany near the Dutch and Belgian borders; formerly it was Charlemagne's northern capital
a large and densely populated urban area; may include several independent administrative districts