Interjections. What is an interjection?. An interjection is a word used to express emotion.. Rats!. Ouch!. Hey!. Now everyone say it together.. Interjections. How does it look in a sentence?. An interjection has no grammatical relation to the rest of the sentence. Usually an interjection is followed by an exclamation point, but sometimes it is set off by a comma or commas. .