city vs San Francisco

city and San Francisco both are nouns.

Word	Noun	Adjective	Verb	Adverb
city	Yes	No	No	No
San Francisco	Yes	No	No	No

city (noun)	San Francisco (noun)
people living in a large densely populated municipality	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
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter