city vs Koln

city and Koln both are nouns.

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

city (noun)	Koln (noun)
people living in a large densely populated municipality	a commercial center and river port in western Germany on the Rhine River; flourished during the 15th century as a member of the Hanseatic League
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter