define interjection in grammar
In grammar, an interjection or exclamation is a word used to express a particular emotion or sentiment on the part of the speaker (although most interjections have clear definitions). Filled pauses such as uh, er, um are also considered interjections. Interjections are often placed at the beginning of a sentence. An interjection is sometimes expressed as a single word or non-sentence phrase, followed by a punctuation mark. The isolated usage of an interjection does not represent a complete sentence in conventional English writing.