Theatre
The word comes originally from the Greek Theatron, meaning roughly, 'a place for viewing'. In American English, the word 'theater' can mean either a place where films are shown (this is also called a cinema) or a place where live stage plays are performed. In British English, 'theatre' means a place where live plays are performed.  Some people, both English and American, use the spelling 'theatre' to mean a place where live plays are performed, and the spelling 'theater' to mean a cinema.