A building with multiple screens where movies are shown is an example of a movie theater.
Going to see a play is an example of going to the theater.
A person who stars in movies and plays is an example of someone who is in theater.
An operating theater at a medical school.
The European theater during World War II.
A commander in the Southern Pacific theater.
A play that is good theater.
His grandfather was in the Pacific theater during the war.
This man is about to die, get him into theater at once!
I worked in the theater for twenty-five years.
Origin of theater
- Middle English theatre from Old French from Latin theātrum from Greek theātron from theāsthai to watch from theā a viewing
From American Heritage Dictionary of the English Language, 5th Edition