What is the definition of an expletive?

The definition that identifies an expletive as "an oath or exclamation that is profane or obscene" highlights the common understanding of the term in colloquial language. Expletives are often seen as strong, emotional words used to express feelings such as anger, surprise, or frustration, and they may be considered offensive or vulgar. This aligns with the cultural perception of expletives primarily being curse words or profanities that reflect intense emotions.

While other options present valid terms in English language studies, they do not fully encompass the essence of what an expletive is in the context of language use. The option that describes an expletive as an "expression of joy or celebration" deviates from the typical function of expletives, as these expressions are generally more neutral or positive than the strong language associated with expletives. The choice that defines it as "a grammatical term for an unnecessary word" describes a different concept applicable in syntax, while equating it with "a synonym for an adjective" is unrelated to the core understanding of expletives. Therefore, the choice that accurately reflects the nature of expletives as potentially profane or obscene is the most appropriate definition.