to respond to a stimulus by taking appropriate action

to provide a response or justification to counter an accusation or criticisms

to meet a demand or expectation

to correspond with or to be consistent with something

to take responsibility for an action or to be held accountable for it

to be adequate or sufficient for fulfilling a particular function

a solution to a problem or a way out of a predicament

the speech act of replying to a question

a nonverbal reaction

the principal pleading by the defendant in response to plaintiff's complaint; in criminal law it consists of the defendant's plea of `guilty' or `not guilty' (or nolo contendere); in civil law it must contain denials of all allegations in the plaintiff's complaint that the defendant hopes to controvert and it can contain affirmative defenses or counterclaims