certified has 2 distinct synonyms spread across 2 of its 3 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 uncertified.
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.
endorsed authoritatively as having met certain requirements
“a certified public accountant”
fit to be certified as insane (and treated accordingly)
holding appropriate documentation and officially on record as qualified to perform a specified function or practice a specified skill
“a registered pharmacist”
Synonyms, antonyms and the broader and narrower relations for certified come from Princeton University’s WordNet. Full sources and licences.