little theater vs little theatre

little theater and little theatre both are nouns.

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

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

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

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