commutation has 4 distinct synonyms spread across 3 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a warrant substituting a lesser punishment for a greater one
(law) the reduction in severity of a punishment imposed by law
the act of putting one thing or person in the place of another: "he sent Smith in for Jones but the substitution came too late to help"
Synonyms, antonyms and the broader and narrower relations for commutation come from Princeton University’s WordNet. Full sources and licences.