certain Definition

certain
adj

1. Proved or known beyond doubt.

Example: It is certain that the defendant knew Mr Wilson
Thesaurus: sure, conclusive, definite, true, irrefutable, incontestable, absolute, unequivocal, undeniable, indubitable; Antonym: doubtful, uncertain, dubious.
2. Having no doubt about it; absolutely sure.

Thesaurus: confident, assured, positive, convinced, secure, unconcerned; assertive, cocksure; Antonym: troubled.
Form: certain about something (sometimes)
Form: certain of something
3. Used with reference to the future: definitely going to happen, etc; able to rely on or be relied on.
4. Particular and, though known, not named or specified.

Example: a certain friend of yours
5. Used before a person's name to indicate either their obscurity or one's own unfamiliarity with them.

Example: a certain Mrs Smith
6. Said of a quality: undeniably present without being clearly definable.

Example: The beard gave his face a certain authority
7. Some, though not much.

Example: That's true to a certain extent

pronoun

1. Some.

Example: Certain of the team are not pulling their weight

Idiom: for certain

Definitely; without doubt.
Thesaurus: without doubt, absolutely, certainly, for sure.

Idiom: make certain of something

To take action so as to ensure it or be sure about it.

Etymology: 13c: French, from Latin certus sure.