certain.
Sure in one's mind, positive; absolutely confident in the truth of something.
Meaning & usage
Sure in one's mind, positive; absolutely confident in the truth of something.
I was certain of my decision.
Not to be doubted or denied; established as a fact.
Now that more experiments have been run, the theory is certain and the argument is settled.
Sure to happen, inevitable; assured.
It is certain that Spain will reach the finals. / Spain is now certain to reach the finals. / Spain is now certain of a place in the finals.
Bankruptcy is the certain outcome of your constant gambling and lending.
Unfailing; infallible.
Fixed; regular; determinate.
at certain intervals
Particular and definite, but unspecified or unnamed; used to introduce someone or something without going into further detail.
Every wine has a certain distinctive character which sets it apart from all others.
Each morning, she would see a certain man rush past her window on his way to work.
Used to denote that the speaker is referring to a specific person or thing that they do not want to name directly, implying that the listener should infer the identity of the referent.
I would have been here on time, but a certain someone lost the car keys!
Named but not previously mentioned.
Looking inside the cover, they learned that the book had once belonged to a certain R. Jones.
Used before the name of someone famous that people are expected to know.
Since the last British government to make such a proposal was that of a certain Margaret Thatcher, it might not seem unreasonable.
Determined; resolved.
Where this word comes from
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”).
Having been determined but not specified.
Certain people are good at running.
Where this word comes from
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”).
Unnamed or undescribed members (of).
She mentioned a series of contracts, of which certain are not cited.
Where this word comes from
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”).
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Definitions, grammatical labels, IPA, etymology and examples: Wiktionary contributors, extracted by Kaikki / Wiktextract. Adapted under CC BY-SA 4.0. Selected fields and authored examples are shown; third-party quotations and audio are omitted. See contributor history.
Last enriched 2026-09-10. Definitions are in English. Romanizations are shown when supplied by the source; syllable estimates are omitted for unsupported scripts.