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Modal Verbs of Deduction and Speculation in the Past

Hi again, everyone!


Today we are going to look at modal verbs of deduction and speculation in the past.
These modal verbs of deduction in the past are often confusing and difficult to remember, but with a little hard work and practice, you will learn how to use them correctly!


Firstly, it’s important to remember what modal verbs are and why they are used. You can find out more about that by reading this post on the ABA English teachers’ blog.

Now that you’ve refreshed your memory, let’s take a look at how to form and use modal verbs in the past.


When we use a modal verb to talk about a situation where we are not expressing a fact but we are using deduction, the form is MODAL VERB + have + past participle.

Must have + past participle

We use “must have” + a past participle when we are quite sure about something or we can see the evidence of something.

Practice for your TOEFL exam with Magoosh.


You must have gone to bed late; you look tired!

Kevin must have been worried when he lost his car keys at the party.

Might have + past participle

We use “might have” + a past participle when we are not sure about something but we think it was possible.


Sarah might have lost her way; she should be here by now.

Jacob and Claire might have arrived at the party already, but they haven’t called me so I’m not sure. 

Could have + past participle

We use “could have” + a past participle to indicate that someone had the ability or chance to do something  but did not do it. For example,


You could have gone to university but you decided to work instead.

I didn’t know my parents would be asleep when I got home. I could have stayed out longer!

Should have + past participle

We use “should have” + a past participle to express regret or to tell someone off.


You should have studied more! If you had, you would have passed your exam.

shouldn’t have gone out last night; now I’m too tired to study.




Author Bio: This post was written by Brandon, a teacher from ABA English. ABA English–the American & British Academy–is an online academy specializing in teaching English with a unique learning methodology based on the principles of natural learning methods. ABA English teaches you English through short films that take place in real-life situations with  144 free video classes. Go to ABA English and start improving your English with your free 144 video classes.



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