adjustment has 9 distinct synonyms spread across 5 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.
making or becoming suitable; adjusting to circumstances
the act of making something different (as e.g. the size of a garment)
the process of adapting to something (such as environmental conditions)
an amount added or deducted on the basis of qualifying circumstances
“an allowance for profit”
Synonyms, antonyms and the broader and narrower relations for adjustment come from Princeton University’s WordNet. Full sources and licences.