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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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Comments

I reluctantly agreed to a postponement on condition that the sale should be completed and the boat handed over by 31st August.

You may borrow the book on condition that you return it tonight

Teacher, why is "should" used in 1st sentence but not in 2nd sentence?

Thanks for your reply in advance.

It's ten o'clock. Dad might have finished his work. Or
It's ten o'clock. Dad might have finished his work.

Which one is correct ? Or Both are correct ?

Hello Abhishek,

Your sentences are the same. I think you may have made a mistake in your question.

 

Peter

The LearnEnglish Team

Dear teahcers,
Can you explain what is difference between may have, might have or could have? Namely, I want to know difference between them like your explanation about ' may, might and could ' in first paragraph.
Thanks a lot in advance

Hello Ana Silvo

There's no difference in meaning between them. 'might' is a little more common in speaking and 'may' a little more in writing, but people often say 'may' and often write 'might'.

Note that each of these modal verbs can be used in other situations, and in some of those situations, they don't mean the same thing. But here in the context of probability they do.

All the best

Kirk

The LearnEnglish Team

Sir, can I use modal verbs for future like

"He may have gone by tomorrow 2.00 PM."

Hello Amit shukla

Yes, that sentence is grammatically correct, though I would recommend thinking of 'may' as expressing possibility more than the future.

Please note that when you post a comment, it is not published right away. Please don't post the same comment twice; we'll be able to respond more quickly!

All the best

Kirk

The LearnEnglish Team

Hi teacher, I have one sentence about possibility in the past and I just want to know if it’s right or wrong “ His math may have improved by the time the exam came “ Thank you .

Hi Rany,

The sentence is perfectly fine. It tells us that the speaker does not know if the person's maths improved or not, but that it was possible. The meaning is the same as might have and could have in this context.

 

Peter

The LearnEnglish Team

Dear sir
We all know that modals have not indicate tenses, and they only reflect four different aspects of simple, continoues, perfect and perfect continoues. Base of this assumption why in some parts you keep saying this modal use for past certainty, for example they must have practiced too much. But at this example we can not say it is only reflect past tense, it might refer to future or present base on the time phrase used with it , for example
For future, they must have practiced well by tomorrow morning.
For present, they must have practiced well by now.
For past, they must have practiced well already.

Would you please tell me if i am thinking in a right way.
Sincerely Aria

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