replace has 7 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.
substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)
“He replaced the old razor blade”
take the place or move into the position of
“Smith replaced Miller as CEO after Miller left”
Synonyms, antonyms and the broader and narrower relations for replace come from Princeton University’s WordNet. Full sources and licences.
put in the place of another; switch seemingly equivalent items
“the con artist replaced the original with a fake Rembrandt”