valid

Synonyms: accurate attested authentic authoritative binding bona fide cogent compelling conclusive confirmed convincing credible determinative efficacious efficient good in force irrefutable just kosher lawful legal legit legitimate logical official original persuasive potent powerful proven pure solid sound stringent strong substantial telling tested true trustworthy ultimate unadulterated unanswerable uncorrupted weighty well-founded wellgrounded

Antonyms: invalid unacceptable unreal unsound wrong