commutation of sentence, in criminal law, reduction of a sentence for a criminal act by action of the executive head of the government. Like pardon, commutation of sentence is a matter of grace, not of right; it is distinguished from pardon, however, in that the conviction of crime is not nullified. The commutation, hence, may be granted on condition that the criminal observe certain restrictions for the balance of his original sentence. Many states have statutes providing for commutation of sentence as a reward for good conduct during imprisonment. Once earned, the commutation becomes a matter of right and may be enforced by court action.