reenforcement has 2 distinct synonyms spread across 2 of its 2 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.
information that makes more forcible or convincing
“his gestures provided eloquent reinforcement for his complaints”
a military operation (often involving new supplies of men and materiel) to strengthen a military force or aid in the performance of its mission
“they called for artillery support”
Synonyms, antonyms and the broader and narrower relations for reenforcement come from Princeton University’s WordNet. Full sources and licences.