substantiation has 5 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.
additional proof that something that was believed (some fact or hypothesis or theory) is correct
“fossils provided further confirmation of the evolutionary theory”
the act of validating; finding or testing the truth of something
Synonyms, antonyms and the broader and narrower relations for substantiation come from Princeton University’s WordNet. Full sources and licences.