down town vs hub

down town and hub both are nouns.

Word	Noun	Adjective	Verb	Adverb
down town	Yes	No	No	No
hub	Yes	No	No	No

As nouns, hub is a hypernym of down town; that is, hub is a word with a broader meaning than down town:

down town: the center of a city
hub: a center of activity or interest or commerce or transportation; a focal point around which events revolve

down town (noun)	hub (noun)
the center of a city	the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes
	a center of activity or interest or commerce or transportation; a focal point around which events revolve