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once - definition and synonyms

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adverb, conjunction, noun     once pronunciation in British English
Once can be used in the following ways:
as an adverb: I only met him once.They’ve been here once before.
as a conjunction: Once you get there, you’ll love it.
as a noun (after ‘for’ or ‘at’): For once I wish you’d tell me the truth. (after ‘the’, ‘this’, or ‘that’): Yes, I met him, but just the once.
  1. 1
    on one occasion only

    Cathy’s only been to visit us once.

    I’d seen the show once before, but I enjoyed seeing it again.

    I’m only going to say this once, so listen carefully.

    (just) the once (=on one particular occasion only):

    We met just the once, but I still remember him very clearly.

  2. 2
    used for saying that a particular situation existed at a time in the past, but it does not exist any longer

    Did you know that Dan was once a policeman?

    Louise bought the house where her grandparents had once lived.

    The once mighty US car industry was now facing strong competition from abroad.

    1. a.
      used for saying that something happened at some time in the past

      Once we drove all the way to Edinburgh with four little kids in the back seat.

      I once taught myself to knit, and I was pretty good at it.

  3. 3
    used for saying that as soon as one thing happens, something else happens

    Once we were through the gates, she went off and left me on my own.

    I’m sure you’ll be very happy here once you get to know everyone.

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to manipulate someone psychologically so that they begin to question their own perceptions and memories

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Dunning-Kruger effect

the phenomenon by which an incompetent person is too incompetent to understand his own incompetence

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