waterfront vs city district

waterfront and city district both are nouns.

Word	Noun	Adjective	Verb	Adverb
waterfront	Yes	No	No	No
city district	Yes	No	No	No

As nouns, city district is a hypernym of waterfront; that is, city district is a word with a broader meaning than waterfront:

waterfront: the area of a city (such as a harbor or dockyard) alongside a body of water
city district: a district of a town or city

waterfront (noun)	city district (noun)
the area of a city (such as a harbor or dockyard) alongside a body of water	a district of a town or city