theater vs region

theater and region both are nouns.

Word	Noun	Adjective	Verb	Adverb
theater	Yes	No	No	No
region	Yes	No	No	No

As nouns, region is a hypernym of theater; that is, region is a word with a broader meaning than theater:

theater (noun)	region (noun)
a building where theatrical performances or motion-picture shows can be presented	a part of an animal that has a special function or is supplied by a given artery or nerve
the art of writing and producing plays	a knowledge domain that you are interested in or are communicating about
a region in which active military operations are in progress	the extended spatial location of something
	a large indefinite location on the surface of the Earth
	the approximate amount of something (usually used prepositionally as in `in the region of')