## Examples
- I am certain that I locked the door.
- It is certain that prices will rise next year.
- Certain people in the room disagreed with the plan.

## Synonyms
- assured
- clear
- confident
- definite
- doubtless
- positive
- sicker
- sure
- unambiguous
- unequivocal
- univocal
- unwavering

## Antonyms
- impossible
- incidental
- uncertain

## Derived Forms
- certainly
- certainness
- certainty
- noncertain

## Related Forms
- fated
- intentional
- irrefutable

## Roots and Affixes
- Root: *krey-
- Root: certeyn
- Root: certain
- Root: certus

## Etymology
From Middle English certeyn, certein, certain, borrowed from Old French certain, from a Vulgar Latin unattested form *certānus, extended form of Latin certus (“fixed, resolved, certain”), of the same origin as cretus, past participle of cernere (“to separate, perceive, decide”). Displaced native Middle English wis, iwis (“certain, sure”) (from Old English ġewiss (“certain, sure”)) and alternative Middle English spelling sertane (“some, certain”).

## AI Etymology
certain is an adjective. It is from Middle English certeyn, certein, certain, borrowed from Old French certain, from a Vulgar Latin unattested form *certānus, extended form of Latin certus (“fixed, resolved, certain”), of the same origin as cretus, past participle of cernere (“to separate, perceive, decide”). Displaced native Middle English wis, iwis (“certain, sure”) (from Old English ġewiss (“certain, sure”)) and alternative Middle English spelling sertane (“some, certain”). Historical forms in the chain include *krey- (Proto-Indo-European), certeyn (Middle English), certain (Old French), and certus (Latin). Current senses include completely sure that something is true, sure to happen and impossible to avoid, and particular but not named or described in detail. Derived forms include certainly, certainness, certainty, and noncertain. Related words include fated, intentional, and irrefutable.

## Topics
- Describing Qualities

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