Modal Verbs of Deduction – Must/Can’t/May (not) & Might (not)

In English, there are several modal verbs of deduction. They allow us to guess if something is true based on the information available. Four very important ones to know are must, can’t, may (not), and might (not).[1]https://learnenglish.britishcouncil.org/grammar/intermediate-to-upper-intermediate/modals-deductions-about-the-present

modal verbs of deduction

Must

You use the word “must” when you are 100% (or nearly) positive that something is true.[2]https://smitkit10-11.weebly.com/deduction.html

For example:

  • You must be tired after that workout. (I am very sure that you are tired)
  • I don’t have my phone. It must be on my desk. (I am sure that the phone is on my desk)
  • She must study for the test if she wants to do well. (I am very sure that if she wants to pass the test it is required that she study)

May (not) & Might (not)

You use the words “may (not)” or “might (not)” if you are 50% sure of a fact.

For example:

  • They are not here yet. They might be stuck in track. (I am not exactly sure why they aren’t here)
  • Frank may be able to help us with the problem. (There is a 50% chance that Frank can help)
  • The airline told us that the flight might be delayed due to weather. (There is a 50% chance that the flight gets delayed due to weather)

Difference between Might and May

May is used for situations that could be factual or could be possible.

Might is used for speculative situations that didn’t actually happen.[3]https://writingexplained.org/may-vs-might-difference

Can’t

You use the word “can’t” when you are 100% (or nearly) sure that something is false.[4]https://www.test-english.com/explanation/b1/modal-verbs-deduction-must-might-cant/

For example:

  • Sorry, I can’t do that. It’s against the law. (I am 100% unable to do the task)
  • You can’t stay in the house while they paint it. The fumes are toxic. (You are 100% not allowed to be in the house)
  • I can’t drive today. I just had an eye test and can’t see. (Due to the eye test, I am 100% unable to drive)

Example Exercises

 13%

Question 1 of 8

1. Do you know where my wallet is? It _____ be in the house because I remember paying for lunch today.

Question 1 of 8

Question 2 of 8

2. That is an expensive gift! Your fiancée _____ be rich!

Question 2 of 8

Question 3 of 8

3. You _____ be a great student. You are always getting good grades.

Question 3 of 8

Question 4 of 8

4. You seem too know a lot about that subject. You _____ really enjoy reading about it.

Question 4 of 8

Question 5 of 8

5. I _____ not be able to make the party. I think my boss is going to make me stay late at work.

Question 5 of 8

Question 6 of 8

6. It _____ rain tomorrow.

Question 6 of 8

Question 7 of 8

7. Why did they give him the promotion over her? He has only been here a month! He _____ know more than her about how the company works.

Question 7 of 8

Question 8 of 8

8. I have been extremely tired at work lately. I _____ be working too hard.

Question 8 of 8


 

Modal Verbs: can/can’t/could/couldn’t/would/wouldn’t

Modal verbs are helping verbs that express obligation, permission, possibility, and ability.[1]https://www.gingersoftware.com/content/grammar-rules/verbs/modal-verbs/

Can/Can’t

“Can” is used in many different situations.

Positive

Subject + can + base verb

Negative

Subject + can’t + base verb

Question

Can + subject + base verb

When do you use it?

Possibility

  • I can run very fast.
  • She can speak French
  • They can visit us.

Impossibility

  • We can’t eat that food.
  • He can’t call us.
  • It can’t be done.

Ask for Permission

  • Can you help me with my homework?
  • Can they come with us?
  • Can we get ice cream?

Give Permission

  • You can eat some dessert.
  • They can come to our house.
  • She can borrow our car.

Could/Couldn’t

In the present tense, the modal verb “could” is used to:

Ask for Permission

Could + subject + base verb (this is a polite way to ask for permission)

  • Could I talk to her?
  • Could I have their number?
  • Could I have an appointment?

Give a Suggestion

 Subject + could + base verb

  • You could fly tomorrow.
  • You could ask the manager.
  • You could take the tour of the park tomorrow.

Would Like/Wouldn’t Like

The modal of “would like” is used to show if someone is interested in something (object).

Positive

Subject + would like + object

Negative

Subject + wouldn’t like + object

Question

Would + subject + like + object

Would Like To/Wouldn’t Like To

The modal of “would like to” shows if someone is interested in doing something (action).

Positive

Subject + would like + to + infinitive

Example:

  • I would like to swim right now.
  • She would like to eat lunch.
  • They would like to visit us next summer.

Negative

Subject + wouldn’t like + to + infinitive

Example:

  • I wouldn’t like to go there by myself.
  • John wouldn’t like to meet you.
  • We wouldn’t like to eat vegetables.

Question

Would + subject + like to + infinitive?

  • Would you like to come with me?
  • Would they like to eat dinner with us?
  • Would she like to talk?

Practice Exercises

Please go to Modal Verbs: can/can’t/could/couldn’t/would/wouldn’t to view this quiz