WordNet records no synonym and no antonym for reinstatement. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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 condition of being reinstated
“her reinstatement to her former office followed quickly”
the act of restoring someone to a previous position
“we insisted on the reinstatement of the colonel”
Synonyms, antonyms and the broader and narrower relations for reinstatement come from Princeton University’s WordNet. Full sources and licences.