contraction has 4 distinct synonyms spread across 2 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. Its one recorded opposite is expansion.
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.
(physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber)
the process or result of becoming smaller or pressed together
“the contraction of a gas on cooling”
a word formed from two or more words by omitting or combining some sounds
“`won't' is a contraction of `will not'”
Synonyms, antonyms and the broader and narrower relations for contraction come from Princeton University’s WordNet. Full sources and licences.