home theatre vs home theater

home theatre and home theater both are nouns.

Word	Noun	Adjective	Verb	Adverb
home theatre	Yes	No	No	No
home theater	Yes	No	No	No

As nouns, home theatre and home theater are synonyms defined as:

home theatre and home theater: television and video equipment designed to reproduce in the home the experience of being in a movie theater

home theatre (noun)	home theater (noun)
television and video equipment designed to reproduce in the home the experience of being in a movie theater	television and video equipment designed to reproduce in the home the experience of being in a movie theater