late Middle English: via Old French from Latin interjectio(n-), from the verb interjicere (see interject)
A word or phrase that expresses emotion, typically in an abrupt or emphatic way. It is not connected grammatically to the rest of the sentence. When the emotion expressed is very strong, the interjection is followed by an exclamation point. Otherwise it is followed by a comma:Stop! I can’t let you in here. Yeah! Dempsey has won another fight. Ah, that was a wonderful meal. No, I don’t think that’s true.