response

A response is a reply or an answer—something said or done after someone else has said or done something.

Like response, reply and answer can be used in the context of verbal responses (such as in speech or writing) as well as actions. The word acknowledgement refers to a response that simply acknowledges an initial message or action (as opposed to one that consists of new information or an action on the part of the one responding).

Some responses come in the form of feedback.

A reply to a comment—especially a quick and witty reply—is sometimes called a comeback, retort, rejoinder, or riposte.

A response to an invitation is popularly called an RSVP, an abbreviation of the French phrase répondez s’il vous plaît, meaning “please respond.”

In military and sports contexts, the word response is sometimes used as a general way of referring to a counterattack or counterstroke.

Response is perhaps slightly more formal than its synonyms answer and reply, but there isn’t a more formal word that is commonly used.

The more formal word rejoinder is sometimes used in specific legal contexts.

A formal (as in an official) response is sometimes called a formal reply or an official reply.

The opposite of a response is a nonresponse—when someone doesn’t reply or answer at all. The term lack of response is often used.

In another sense, the opposite of a response could be thought of as the initial question, statement, comment, email, etc.—since this is what the response responds to.

Response is spelled with an s, which you can also see in the related words responsive, responsible, and responsibility.