certainty
n. C / Un. the state of being completely sure about something. It can also mean a fact that is definitely true and will happen.
n. the state of being free from doubt or the quality of being reliably established. Often functions as an abstract concept or as a concrete instance of an inevitable event.
I can say with certainty that we will win.
The scientists cannot predict the exact date of the eruption with absolute certainty, though they know it is coming.
In an era of rapid technological change, the only certainty is that the job market will look fundamentally different in a decade than it does today.
From Middle English certeynte (“surety”), from Anglo-Norman certeinte, from Old French certeinete, from Vulgar Latin *certānitās, from Latin certus.
Uncountable when referring to the general state of being sure; countable when referring to a specific fact or event that is certain.