Other forms: certainties
Certainty is being completely sure, with no doubt left anywhere in your head. Knowing with certainty that you locked the door; the calm of someone who has checked the figures twice and has no wish to check again.
It counts as well: a certainty is a thing bound to happen. A win on Saturday is now a certainty, and there are no certainties in this business. Fixed phrases carry most of its weight — with absolute certainty, with any certainty, a mathematical certainty. The opposite is uncertainty, and its close neighbour is doubt. Mind the shapes: certainty is the noun, certain the adjective, certainly the adverb you use to agree with somebody.
1nouncertaintyThe state of being completely sure about something.
“Nobody can say with certainty how long the repairs will take.”
synonyms: conviction, assurance
2nounhappenSomething that is sure to happen or sure to be true.
“Rain in October is a certainty here.”
certainty is a state of mind.
Certainty arrived as Middle English certeynte, a surety or a guarantee, from Anglo-Norman certeinte and Old French certeinete. Behind those sits a Vulgar Latin *certānitās built on Latin certus, the word that also gives English certain. The oldest sense was a pledge you could rely on rather than a feeling in the mind.
Latin
certus
Vulgar Latin
*certānitās
Old French
certeinete
Anglo-Norman
certeinte
Middle English
certeynte — surety
English, today
certainty
From Middle English certeynte (“surety”), from Anglo-Norman certeinte, from Old French certeinete, from Vulgar Latin certānitās, from Latin certus.
Etymology from Wiktionary, CC BY-SA