theater vs act

theater and act both are nouns.

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

theater (noun)	act (noun)
a building where theatrical performances or motion-picture shows can be presented	something that people do or cause to happen
the art of writing and producing plays	a subdivision of a play or opera or ballet
a region in which active military operations are in progress	a legal document codifying the result of deliberations of a committee or society or legislative body
	a short performance that is part of a longer program
	a manifestation of insincerity

theater (verb)	act (verb)
	behave in a certain manner; show a certain behavior; conduct or comport oneself
	pretend to have certain qualities or state of mind
	discharge one's duties
	play a role or part
	perform on a stage or theater
	behave unnaturally or affectedly
	perform an action, or work out or perform (an action)
	have an effect or outcome; often the one desired or expected
	be suitable for theatrical performance