city vs Sao Louis

city and Sao Louis both are nouns.

Word	Noun	Adjective	Verb	Adverb
city	Yes	No	No	No
Sao Louis	Yes	No	No	No

city (noun)	Sao Louis (noun)
people living in a large densely populated municipality	a city on an offshore island in northeast Brazil
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter