urban center vs Liepaja

urban center and Liepaja both are nouns.

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

urban center (noun)	Liepaja (noun)
a large and densely populated urban area; may include several independent administrative districts	a city of southwestern Latvia on the Baltic Sea