city vs Mumbai

city and Mumbai both are nouns.

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

city (noun)	Mumbai (noun)
people living in a large densely populated municipality	a city in western India just off the coast of the Arabian Sea; India's 2nd largest city (after Calcutta); has the only natural deep-water harbor in western India
a large and densely populated urban area; may include several independent administrative districts
an incorporated administrative district established by state charter