recognize has 15 distinct synonyms spread across 8 of its 9 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.
accept (someone) to be what is claimed or accept his power and authority
“The Crown Prince was acknowledged as the true heir to the throne”
detect with the senses
“The fleeing convicts were picked out of the darkness by the watchful prison guards”
express greetings upon meeting someone
express obligation, thanks, or gratitude for
“We must acknowledge the kindness she showed towards us”
exhibit recognition for (an antigen or a substrate)
Synonyms, antonyms and the broader and narrower relations for recognize come from Princeton University’s WordNet. Full sources and licences.