little theatre vs little theater

little theatre and little theater both are nouns.

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

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

little theatre and little theater: a small theater for experimental drama or collegiate or community groups

little theatre (noun)	little theater (noun)
a small theater for experimental drama or collegiate or community groups	a small theater for experimental drama or collegiate or community groups