From Middle English certeynte, from Anglo-Norman certeinte, from Old French certeinete, from Vulgar Latin *certānitās, from Latin certus.

• (America) IPA: /ˈsɝtn̩ti/
• (RP) IPA: /ˈsɜːtn̩ti/

certainty

1. The state of being certain.

   Synonyms: certitude, sureness

   Antonyms: doubt, uncertainty

2. An instance of being certain.
3. A fact or truth unquestionably established.

   Synonyms: Thesaurus:sure thing

   • 1824, Walter Savage Landor, Imaginary Conversations of Literary Men and Statesmen, volume I, London: […] Taylor and Hessey, […], →OCLC ↗:

     Certainties are uninteresting and sating.

• French: certitude
• German: Gewissheit
• Italian: certezza
• Portuguese: certeza
• Russian: уве́ренность
• Spanish: certeza