urban center vs Colon

urban center and Colon both are nouns.

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

urban center (noun)	Colon (noun)
a large and densely populated urban area; may include several independent administrative districts	a port city at the Caribbean entrance to the Panama Canal