the art of writing and producing plays
"After years of working as a playwright, she finally found her place in theatre through collaborations with local directors."
a region in which active military operations are in progress
"the army was in the field awaiting action"
"he served in the Vietnam theater for three years"
Alternative spelling of theater
"She booked tickets for a play at the local theatre last night."
In plain English: A theatre is a building with a stage where actors perform plays and other shows for an audience to watch.
"We went to the theatre last night to see a new play."
Usage: Use this British English spelling when referring to live dramatic performances or cinema venues in non-American contexts, while American writers should use the variant theater. Both spellings refer to the same concept and are interchangeable depending on regional preference.
The word "theatre" comes from the Latin theatrum, which was borrowed into English via Old French. It originally described a Greek structure called théatron, meaning simply "a place for viewing."