city vs Pisa

city and Pisa both are nouns.

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

city (noun)	Pisa (noun)
people living in a large densely populated municipality	a city in Tuscany; site of the famous Leaning Tower
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter