Pergamum vs urban center

Pergamum and urban center both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pergamum	Yes	No	No	No
urban center	Yes	No	No	No

Pergamum (noun)	urban center (noun)
an ancient Greek city located in the western part of what is now modern Turkey; the technique of preparing sheepskins as parchment was developed here	a large and densely populated urban area; may include several independent administrative districts