modification has 5 distinct synonyms spread across 3 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.
the act of making something different (as e.g. the size of a garment)
Synonyms, antonyms and the broader and narrower relations for modification come from Princeton University’s WordNet. Full sources and licences.
slightly modified copy; not an exact copy
“a modification of last year's model”
the grammatical relation that exists when a word qualifies the meaning of the phrase
an event that occurs when something passes from one state or phase to another
“the change was intended to increase sales”