commitment has 6 distinct synonyms spread across 4 of its 5 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.
the trait of sincere and steadfast fixity of purpose
“a man of energy and commitment”
the act of binding yourself (intellectually or emotionally) to a course of action
“his long commitment to public service”
an engagement by contract involving financial obligation
“his business commitments took him to London”
a message that makes a pledge
the official act of consigning a person to confinement (as in a prison or mental hospital)
Synonyms, antonyms and the broader and narrower relations for commitment come from Princeton University’s WordNet. Full sources and licences.