urban center vs San Francisco

urban center and San Francisco both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
San Francisco	Yes	No	No	No

urban center (noun)	San Francisco (noun)
a large and densely populated urban area; may include several independent administrative districts	a port in western California near the Golden Gate that is one of the major industrial and transportation centers; it has one of the world's finest harbors; site of the Golden Gate Bridge