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Modals in the Present and Past

📑 5 slides 👁 14 views 📅 10/16/2026
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How Modals Express Meaning

Modal verbs communicate attitudes such as obligation, advice, certainty, possibility, and prohibition.

How Modals Express Meaning
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Obligation, Advice, and Prohibition

  • Use must or have to for present obligation: We must respect the law; past obligation uses had to.
  • Should and ought to give advice; for past advice or regret, use should have or ought to have plus a past participle.
  • Mustn’t prohibits an action now, as in You mustn’t smoke here; it does not mean lack of necessity.
  • For past prohibition or criticism, mustn’t have plus a past participle can describe an unacceptable action.
Obligation, Advice, and Prohibition
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Certainty and Impossibility

  • Must expresses a strong present deduction: a person living in a large villa must be rich.
  • For a strong deduction about the past, use must have plus a past participle: He must have had an accident.
  • Can’t signals that something is impossible or strongly unlikely now: He can’t be American.
  • For past impossibility, use can’t have plus a past participle: She can’t have watched it while she was at school.
Certainty and Impossibility
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Possibility and Lack of Necessity

  • Can, may, and might describe present possibility: Cloudy skies mean it may rain, though it is not certain.
  • Past possibilities use can, could, may, or might have plus a past participle to describe uncertain events.
  • Needn’t and don’t have to show that an action is unnecessary now, such as buying milk already in the fridge.
  • For past lack of necessity, use didn’t need to or didn’t have to: We had plenty of time, so there was no need to hurry.
Possibility and Lack of Necessity
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Choose the Form That Fits

  • Use the base verb after present modals: must stop, should prepare, might rain, and can’t be.
  • Past deductions and advice follow modal plus have plus past participle: must have left, should have studied.
  • Had to describes a past obligation, while didn’t have to describes an action that was not necessary.
  • Check whether the sentence expresses a rule, recommendation, deduction, possibility, or lack of need.
Choose the Form That Fits
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