Grammar Lessons: Modals of Deduction

Modals of Deduction

Modals of Deduction


We use must when we feel sure that something is true because there’s very strong evidence.

  1. He must be around here because his car is parked there
  2. You are pilot, that must be interesting
  3. You have worked all day, you must be tired
  4. He has an expensive car, he must have some money


We use mightmay or could to say that we think something is possible but we’re not sure.

  1. I heard a noise, there might be a cat on the roof
  2.  He might be  in his bedroom
  3. He might be in the Gym,  sometimes he goes there


We use can’t when we feel sure something is not true.

  1. He can’t be dead, I just talked to him on the phone
  2. It can’t be a mechanical problem, the car is new
  3. That can’t  be James, James wears glasses
  4. My wallet can’t be in my backpack, I already checked there

Modals of Deduction Exercises

Exercise #1

Modals of Deduction: Must, Might and Can’t

Choose Must, Might and Can't

Exercise #2

A: Hey, what is the matter with you?

B: Well, I have to tell you something and I think you _________________ like it.

A: Come on! Tell me what it is. It _________________ be that bad.

B: I don’t know. I’m afraid you _________________ react badly.

A: Then I’m sure it _________________ be serious. Please, tell me.

B: I saw Lindsey holding hands with another man.

A: What?

B: Please, I know you 10 __________________ be upset right now, but…

A: Dude, Lindsey and I broke up more than a year ago. Didn’t you know?


Learn More

If you want to learn more about Grammar, consider checking these pages:

  1. Basic User
  2. Independent User
  3. Proficient User