acceptance has 7 distinct synonyms spread across 4 of its 7 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. Its one recorded opposite is rejection.
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 mental attitude that something is believable and should be accepted as true
“he gave credence to the gossip”
the act of accepting with approval; favorable reception
“its adoption by society”
the state of being acceptable and accepted
“torn jeans received no acceptance at the country club”
(contract law) words signifying consent to the terms of an offer (thereby creating a contract)
a disposition to tolerate or accept people or situations
“all people should practice toleration and live together in peace”
the act of taking something that is offered
“her acceptance of the gift encouraged him”
Synonyms, antonyms and the broader and narrower relations for acceptance come from Princeton University’s WordNet. Full sources and licences.