The word “interjection” comes from a Latin word that means “throw between.”
An interjection is a word or phrase that is used alone or thrown into a sentence to express an emotion, for example, Homer Simpson’s “Doh!”
Examples of interjections:
Naughty words called “expletives” are interjections.
Interjections rarely occur in formal writing or speech. They are common in informal spoken English and in written dialog.