San Francisco vs city

San Francisco and city both are nouns.

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

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