Monolinguist

[Oralee]

Well. If you [speak] three [languages], this means you are a trilinguist. If you speak two languages, this means that you are trilinguist. But if you are a monolonguist; thats to say, if you speak one and [only one] language, this means that you are AMERICAN!

[Michiko]

A person who speaks only one language; = monolingual.