city vs Kaluga

city and Kaluga both are nouns.

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

city (noun)	Kaluga (noun)
people living in a large densely populated municipality	a city of central Russia to the south of Moscow
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter