# 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:

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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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

Hello Aria,

Modal verbs have a range of meanings. When 'must' is used for logical deduction it is always a deduction following another action, so the only way to use it in a future context is to create an future condition. You cannot say 'They must have practised well by tomorrow morning' but you could say 'If they win the game tomorrow then they must have been practising hard'.

Note that 'must have' can also be used with other meanings. For example, when we use 'must' for obligation we can use it with future reference. For example, you could say 'When I get back to the office you must have finished this project or there will be trouble!'

Peter

The LearnEnglish Team

Hello Oleg

That could be confusing, since 'could' can mean that you are able to do it, which implies that you are saying you will do it. If you are not sure, it'd be better to use 'might' or to hedge your response a bit, e.g. 'I think I could meet you'.

All the best

Kirk

The LearnEnglish Team

I couldn't care less about that. Is this the second conditional without the condition or does it refer to the past modal for ability? Is it ambiguous? Is it the modal for possibility rather than ability? Can it be both?

Hi sam61

Without knowing the context, it's impossible to say which meaning is intended, because both are possible. Normally the context should make it quite clear.

All the best

Kirk

The LearnEnglish Team

Hi,
A-do you remember me?
B-how could I forget you?
In the second sentence 'could' is used for ability or possibility and which time it refers (present/past/future). Please explain?

Hi jitu_jaga,

I think we've already provided a lot of explanations on this point and can't really continue explaining the same point with yet more examples. Why don't you tell us what you think the meaning is here and we will comment on your idea?

The important thing is not which label (possibility/ability etc) you put on a word, but rather that you understand how it is used in communication.

Peter

The LearnEnglish Team

Ok, thank u Peter.

Hi,
1.How could you do that to me? Here, in this sentence 'could' is used for ability or possibility? and which time does this sentence refer(present/past/future)?
2. What is the difference between possibility and probability?