superposition has 2 distinct synonyms spread across 1 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.
(geology) the deposition of one geological stratum on another
(geology) the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest
(geometry) the placement of one object ideally in the position of another one in order to show that the two coincide
the placement of one thing on top of another
Synonyms, antonyms and the broader and narrower relations for superposition come from Princeton University’s WordNet. Full sources and licences.