Meaning

noun a building where theatrical performances or motion-picture shows can be presented

noun the art of writing and producing plays

noun a region in which active military operations are in progress

originFrom Middle English theater, theatre, from Old French theatre, from Latin theatrum, from Ancient Greek θέατρον (théatron, “a place for viewing”), from θεάομαι (theáomai, “to see, watch, observe”).

Etymology from Wiktionary, CC BY-SA 3.0