Certainty
Etymology
From Latin "certus" (sure, fixed, settled), the past participle of "cernere" (to sift, separate, distinguish, decide) — the same root behind discern, discreet, and secret. Certainty is, at root, what has been sifted out and decided; the metaphor is of separating the settled grain from the chaff of doubt.
noun · /SUR-tun-tee/
The state of being completely sure that something is true.
What it names
Use it to name the feeling of having no doubt — and to remember that the feeling and the fact are two different things.
Example
He spoke with total certainty about a date he had, in fact, misremembered.
Related idea
The reframe worth holding: certainty is a psychological state, not a measure of truth — you can feel certain and be wrong, or know something well and still feel uneasy. Contrast proof, which is a property of the argument rather than a feeling in the arguer.
See also