Synonyms of certainty in English:

certainty


See US English definition of certainty

See UK English definition of certainty

See Spanish definition of certeza

noun

1‘she knew with certainty that he was telling the truth’

SYNONYMS
confidence, sureness, positiveness, conviction, certitude, reliability, assuredness, assurance, validity, conclusiveness, authoritativeness, truth, fact, factualness
ANTONYMS

uncertainty, doubt

2‘he accepted defeat as a certainty’

SYNONYMS
inevitability, necessity, foregone conclusion, predictable result, matter of course, racing certainty
certain winner
informal sure thing, cert, dead cert, sure-fire winner
ANTONYMS

possibility, impossibility