bleach has 13 distinct synonyms spread across 2 of its 5 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.
the whiteness that results from removing the color from something
“a complete bleach usually requires several applications”
an agent that makes things white or colorless
the act of whitening something by bleaching it (exposing it to sunlight or using a chemical bleaching agent)
Synonyms, antonyms and the broader and narrower relations for bleach come from Princeton University’s WordNet. Full sources and licences.