urban center vs Bombay

urban center and Bombay both are nouns.

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

urban center (noun)	Bombay (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in western India just off the coast of the Arabian Sea; India's 2nd largest city (after Calcutta); has the only natural deep-water harbor in western India