certainty

Etymology

From Middle English certeynte (“surety”), from Anglo-Norman certeinte, from Old French certeinete, from Vulgar Latin *certānitās, from Latin certus.

noun

1. The state of being certain.
   That there may be Certainty upon an infallible Evidence in Matters of Science, I readily grant you. But since there once were Scepticks in Philosophy as well as Religion, such as doubted of every thing, I very much question, whether the whole World be agreed in this Point; unless you could assure me, that Race of Seekers is now extinct. 1720, Samuel Fancourt, “The Remarker's second Objection produced and examined”, in An Essay Concerning Certainty and Infallibility: Or, Some Reflections Upon a Pamphlet Stiled, “The Nature and Consequences of Enthusiasm Considered, in Some Short Remarks on the Doctrine of the Blessed Trinity Stated and Defended.” In a Letter to the Author of Those Remarks, London: R. Cruttenden, page 35
   The certainty of punishment is the truest security against crimes. October 12, 1786, Fisher Ames, “Lucius Junius Brutus”, in Independent Chronicle
2. An instance of being certain.
3. A fact or truth unquestionably established.
   There is a certainty attainable. A certainty of feeling will arise through the very contemplation of Jesus. But there is also attainable a certainty of Reason. 1895, Alexander Robinson, chapter XXI, in The Saviour in the Newer Light: A Present Day Study of Jesus Christ, Edinburgh, London: William Blackwood & Sons, page 337
   Yet the truth is that City would probably have been coasting by that point if the referee, Michael Oliver, had not turned down three separate penalties, at least two of which could be accurately described as certainties. November 2 2014, Daniel Taylor, “Sergio Agüero strike wins derby for Manchester City against 10-man United”, in guardian.co.uk