substitution has 6 distinct synonyms spread across 2 of its 2 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.
an event in which one thing is substituted for another
“the replacement of lost blood by a transfusion of donor blood”
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 substitution come from Princeton University’s WordNet. Full sources and licences.