urban center vs Tartu

urban center and Tartu both are nouns.

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

urban center (noun)	Tartu (noun)
a large and densely populated urban area; may include several independent administrative districts	a city of southeastern Estonia that was a member of the Hanseatic League