Sometimes, when writing direct speech or a dialogue, there is a scenario where someone will respond with a word or a few words, that do not constitute a full sentence (no subject and no finite verb).
For example:
Person 1: "You can't do that."
Person 2: "Damn!"
The response given by person 2 is not a sentience. And yet, in direct speech, that is sometimes necessary to preserve the flow of regular speech.
Does that sort of language usage have a name to describe it?