urban center vs Kolkata

urban center and Kolkata both are nouns.

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

urban center (noun)	Kolkata (noun)
a large and densely populated urban area; may include several independent administrative districts	the largest city in India and one of the largest cities in the world; located in eastern India; suffers from poverty and overcrowding