co-star vs theater

co-star and theater both are nouns.

Word	Noun	Adjective	Verb	Adverb
co-star	Yes	No	Yes	No
theater	Yes	No	No	No

co-star (noun)	theater (noun)
one of two actors who are given equal status as stars in a play or film	a building where theatrical performances or motion-picture shows can be presented
	the art of writing and producing plays
	a region in which active military operations are in progress

co-star (verb)	theater (verb)
be the co-star in a performance
feature as the co-star in a performance