In grammar, an interjection or exclamation may be a word used to express an 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. Thus, in formal writing, the interjection will be incorporated into a larger sentence clause.Interjection as a figure of speech refers to the use of one word.