Modals of Probability

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What are Modals of Probability?

  • Modals of probability help us express how sure we are about something.

  • The modals of probability are must, might, may, could, and can’t.

    • Chris must have drunk the coffee I made.

    • Gerry might have texted her last night.

    • Susie may join us later.

    • The car could have been stolen at night.

    • The chair can’t have moved itself!

How do we use modals of probability?

  • Must: When we are sure about something we use “must + infinitive (without “to”)”

    • I left my coat on the chair, but Laurie must have moved it. (I don’t know where my coat is, but I feel sure that Laurie is the one who moved it.)

  • Might, may, could: When something is possible but we’re not 100% sure we use “Might/may/could + infinitive (without “to”)”

    • I might have left my coat on the chair. (I don’t remember for sure where I left it.)

    • I may have left my coat on the chair. ( I don’t remember for sure where I left it.

      • Might/may both indicate about the same amount of certainty.

    • I could have left my coat on the chair. (I don’t remember. It’s one possibility out of many.)

      • Could indicates less certainty

  • Can’t, couldn’t: When we are sure that something didn’t happen we use “Can’t/couldn’t + infinitive (without “to”)”

    • Laurie couldn’t have moved my coat. (I feel sure that Laurie did not move my coat.)

    • Laurie can’t have moved my coat. (I feel sure that Laurie did not move my coat.)

      • Couldn’t/can’t both indicate the same amount of certainty.

***Did you know?***

  • You can use modals of probability in the present or the past. When we use modals of probability in the past we add “have.”

    • Present: She must be working right now.

    • Past: She must have been working when we called.

Activity

I. Fill in the blanks with the correct modals of probability

  • Sophia ______________ have changed the oil in her car, but I’m not sure.

  • Jackson _________________ be busy or he would answer my call.

  • Emily _________________ have been in Central Park because she was in France last week.

  • Alexander  ___________________ have been baby-sitting. Do you know if he was?

II. Write or speak (use modals of probability to guess what happened)

Xavier used to love studying English. It was his favorite subject in high school and he studied it during university. Whenever he would meet a native English speaker, he would try to speak with him or her. But lately, Xavier has stopped studying English and doesn’t try to speak it very much. What do you think happened?

Example: He must have gotten discouraged…..

 

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