Definition of certain adjective from the Oxford Advanced Learner's Dictionary

      

    certain

     adjective
    adjective
    BrE BrE//ˈsɜːtn//
     
    ; NAmE NAmE//ˈsɜːrtn//
     
     
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  1. 1  that you can rely on to happen or to be true The climbers face certain death if the rescue today is unsuccessful. certain (that)… It is certain that they will agree. certain to do something She looks certain to win an Oscar. They are certain to agree. certain of something/of doing something If you want to be certain of getting a ticket, book now. Synonymscertainbound sure definite guaranteedThese are all words describing something that will definitely happen or is definitely true.certain that you can rely on to happen or be true:It’s certain that they will agree. They are certain to agree.bound [not before noun] certain to happen, or to do or be something. Bound is only used in the phrase bound to do/​be, etc.:There are bound to be changes when the new system is introduced. You’ve done so much work—you’re bound to pass the exam.sure certain to happen or be true; that can be trusted or relied on:She’s sure to be picked for the team. It’s sure to rain.definite (rather informal) certain to happen; that is not going to change:Is it definite that he’s leaving?guaranteed certain to have a particular result:That kind of behaviour is guaranteed to make him angry.Patterns certain/​sure of something certain/​bound/​sure/​guaranteed to do something certain/​definite that… I couldn’t say for certain/​sure/​definite. Synonymssureconfident convinced certain positive clearThese words all describe somebody who knows without doubt that something is true or will happen.sure [not before noun] without any doubt that you are right, that something is true, that you will get something or that something will happen:‘Is that John over there?’ ‘I’m not sure.’ Are you sure about that? England must win this game to be sure of qualifying. Sure is often used in negative statements and questions, because there is some doubt or anxiety over the matter. If there is no doubt, people often say quite sure:I’m quite sure (that) I left my bag here (= I have no doubt about it).confident completely sure that something will happen in the way that you want or expect:I’m quite confident that you’ll get the job. The team feels confident of winning. Confident is a stronger and more definite word than sure and is more often used in positive statements, when you feel no anxiety.convinced [not before noun] completely sure that something is true or right, especially because the evidence seems to prove it or somebody else has persuaded you to believe it:I’m convinced that she’s innocent.certain [not usually before noun] sure that you are right or that something is true:Are you absolutely certain about this?sure or certain?Like sure, certain is often used in negative statements and questions. It is slightly more formal than sure; sure is more frequent, especially in spoken English.positive [not before noun] (rather informal) completely sure that something is true:She was positive that he’d been there. ‘Are you sure?’ ‘Positive.’clear (often used in negative statements and questions) having no doubt or confusion about something:My memory isn’t really clear on that point.Patterns sure/​confident/​convinced/​certain/​positive/​clear about something sure/​confident/​convinced/​certain of something sure/​confident/​convinced/​certain/​positive/​clear that… sure/​certain/​clear who/​what/​how, etc. to feel sure/​confident/​convinced/​certain/​positive quite/​absolutely/​completely/​fairly/​pretty sure/​confident/​convinced/​certain/​positive/​clear not altogether sure/​confident/​convinced/​certain/​clear
  2. 2  firmly believing something; having no doubts certain (that)… She wasn’t certain (that) he had seen her. certain of/about something Are you absolutely certain about this? certain who/where, etc… I'm not certain who was there. To my certain knowledge he was somewhere else at the time (= I am sure about it).
  3. 3  used to mention a particular thing, person or group without giving any more details about it or them For certain personal reasons I shall not be able to attend. Certain people might disagree with this. They refused to release their hostages unless certain conditions were met.
  4. 4(formal) used with a person’s name to show that the speaker does not know the person It was a certain Dr Davis who performed the operation.
  5. 5  slight; noticeable, but difficult to describe That's true, to a certain extent. I felt there was a certain coldness in her manner.
  6. Express YourselfExpressing certainty or uncertaintyWhen you are stating what has happened or is going to happen, you can say how certain or uncertain you are about what you are saying: I'm sure/100% certain/​absolutely positive I left my keys on the table. There's no doubt in my mind that this is the best option. Without a doubt,/No question, this is where it was. I'm not (at all) sure what time they arrive, to be honest. I rather doubt they'll call back.(British English) Word Origin Middle English: from Old French, based on Latin certus ‘settled, sure’.Extra examples Digby looked certain to be the next president. I don’t know for certain how many people are coming. I grew more and more certain that she was lying to me. I think she’s a teacher, but I couldn’t say for certain. It’s by no means certain that she’ll get the job. Make certain that you lock the door if you go out. He wasn’t certain who he’d given the papers to. I couldn’t say for certain whether she’ll be there. If you want to be certain of getting into the concert, buy your ticket now. It’s certain that they will agree. She wasn’t certain (that) he’d seen her. The climbers face certain death if the rescue attempt is unsuccessful. They are certain to agree. To my certain knowledge he was somewhere else at the time. You have to be quite certain of the facts before making a decision.Idioms  without doubt I can't say for certain when we'll arrive.  to find out whether something is definitely true I think there's a bus at 8 but you'd better call to make certain.
    make certain of something/of doing something
     
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    to do something in order to be sure that something else will happen You'll have to leave soon to make certain of getting there on time.
    if you talk about a person being of a certain age, you mean that they are no longer young but not yet old The show appeals to an audience of a certain age.
See the Oxford Advanced American Dictionary entry: certain