conversion has 4 distinct synonyms spread across 2 of its 9 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 change in the units or form of an expression: "conversion from Fahrenheit to Centigrade"
a successful free throw or try for point after a touchdown
a spiritual enlightenment causing a person to lead a new life
(psychiatry) a defense mechanism represses emotional conflicts which are then converted into physical symptoms that have no organic basis
a change of religion
“his conversion to the Catholic faith”
interchange of subject and predicate of a proposition
act of exchanging one type of money or security for another
the act of changing from one use or function or purpose to another
Synonyms, antonyms and the broader and narrower relations for conversion come from Princeton University’s WordNet. Full sources and licences.