city vs Porto

city and Porto both are nouns.

Word	Noun	Adjective	Verb	Adverb
city	Yes	No	No	No
Porto	Yes	No	No	No

city (noun)	Porto (noun)
people living in a large densely populated municipality	port city in northwest Portugal; noted for port wine
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter