Probability

Level: beginner

Possibility

We use may, might and could to say that something is possible, but not certain:

They may come by car. (= Maybe they will come by car.)
They might be at home. (= Maybe they are at home.)
If we don't hurry, we could be late. (= Maybe we will be late.)

We use can to make general statements about what is possible:

It can be very cold here in winter. (= It is sometimes very cold here in winter.)
You can easily get lost in this town. (= People often get lost in this town.)

Be careful!

We do not use can to talk about specific events:

A: Where's John?
B: I'm not sure. He may/might/could be 
(NOT can) in his office.

Notice the difference in meaning between can and may/might/could:

That dog can be dangerous.
(= Sometimes that dog is dangerous. I know.)

That dog may/might/could be dangerous.
(= Perhaps that dog is dangerous. I don't know.)

can and may/might/could

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Level: intermediate

We use may have, might have or could have to make guesses about the past:

I haven't received your letter. It may have got lost in the post.
It's ten o'clock. They might have arrived by now.
Where are they? They could have got lost.

We use could to make general statements about the past:

It could be very cold there in winter. (= It was sometimes very cold there in winter.)
You could easily get lost in that town. (= People often got lost in that town.)

could and could have

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Impossibility

Level: beginner

We use can't or cannot to say that something is impossible:

That can't be true.
You cannot be serious.

Level: intermediate

We use can't have or couldn't have to say that a past event was impossible:

They know the way here. They can't have got lost!
If Jones was at work until six, he couldn't have done the murder.

Certainty

Level: beginner

We use must to show we are sure something is true and we have reasons for our belief:

It's getting dark. It must be quite late.
You haven’t eaten all day. You must be hungry.

We use should to suggest something is true and we have reasons for our suggestion:

Ask Miranda. She should know.
It's nearly six o'clock. They should arrive soon.

Level: intermediate

We use must have and should have for the past:

They hadn't eaten all day. They must have been hungry.
You look happy. You must have heard the good news.
It's nearly eleven o'clock. They should have arrived by now.

Probability 1

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Probability 2

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Probability 3

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Probability 4

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Probability 5

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Submitted by TJ on Sun, 25/03/2018 - 07:34

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Hi sir, In this sentence 'You could lose your way in the dark. ' , I can't get the aspect. Could you please explain the context . Because I can't understand the usage of could in the past possibility. Thanks

Submitted by Peter M. on Sun, 25/03/2018 - 08:32

In reply to by TJ

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Hi TJ,

It's important to remember that modal verbs have multiple uses. One use of 'could' is as the past form of 'can' to describe possibility. It's helpful to compare the two:

When it is foggy people can easily get lost on their way home.

I lived in Scotland as a child and it was often foggy, so people could easily get lost on their way home.

The first sentence describes something that is generally possible (getting lost) in certain situations (when it is foggy). The second sentence describes something that was generally possible (getting lost) in certain situations (when it was foggy).

 

Peter

The LearnEnglish Team

Submitted by TJ on Sun, 25/03/2018 - 10:12

In reply to by Peter M.

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got it, clear. Thanks for the quick reply. cheers

Submitted by Hamdy Ali on Wed, 10/01/2018 - 19:16

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Hi If I am sure that I did well in exams ,can I say :"I am sure I passed" ? or something else

Submitted by Kirk on Thu, 11/01/2018 - 07:35

In reply to by Hamdy Ali

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Hello Hamdy Ali,

Yes, that is right. Both 'I'm sure' and 'I'm confident' are common ways to experss this. Good work!

All the best,
Kirk
The LearnEnglish Team