# 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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Thanks a lot for the valuable answer to my question sir. I have got another question that some of the people and websites consider "ought to" and "need to" as modal verbs. Are these indeed modal verbs sir?

Hell Vijay Soni,

These are examples of what are called 'semi-modals'. In some aspects they function as modals but in others they are more like 'normal' verbs. For example, modals are usually followed by the bare infinitive (without 'to'), but these verbs have 'to'. Modals do not have regular past forms but rather perfect forms (should > should have), whereas 'need to' has a past form 'needed to'. On the other hand, modals do not have a different third person form (I should > He should), and this is true of 'ought to' (I ought to > He ought to).

There are other examples of semi-modals, such as 'dare'.

Best wishes,

Peter

The LearnEnglish Team

Soumis par Inas Elshinnawy le dim 06/03/2016 - 11:49

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Hi, teachers, It’s ten o’clock. They might have arrived now. Does this sentence suggest that it's a hypothetical situation? meaning that it was possible for them to arrive if they left ,but they didn't?? They could have arrived hours ago. Does this sentence have two meanings? The first is hypothetical like the previous sentence ,and the second is about expressing possibility of a past situation ? I hope that my questions are clear.

Hello Inas,

In your first pair of sentences, the second sentence is hypothetical in one sense, i.e. it's possible they have arrived, but also possibly they haven't – we don't know. But this kind of hypothetical situation is a bit different from the hypothetical situations in, for example, third conditionals.

Regarding the other sentence, which two meanings do you have in mind? I'm afraid I'm not sure I understand what your questions are really about. If there's some specific context, it would be helpful to know that.

All the best,
Kirk
The LearnEnglish Team

Soumis par hikaru tsuki le sam 13/02/2016 - 10:33

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what is the difference between i might come and i might not come? when should i use might not?

Hello hikaru tsuki,

Which of these you use depends on what you consider the current, normal or likely state. For example, if I say 'I might come' then I am suggesting or assuming that the normal situation is not coming, and I am saying that there is a chance of this changing.

As another example, if I look out of the window and say 'It might rain' then I am suggesting that the normal/expect weather is dry, but that rain has become a possiblility.

Best wishes,

Peter

The LearnEnglish Team

Soumis par Karzan_Camus le sam 12/12/2015 - 09:49

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Hello, teachers. I wander if this sentence correct, I mean the use of (might not) to talk about an impossible situation in the past? Here is the sentence (They lost the game yesterday. They might not have played well.)??

Hello Karzan,

You can use 'might not' with 'have played' to speculate about the past, but I wouldn't call that an impossible situation. By the way, another way to speculate about why they lost is: 'Perhaps they didn't play well'.

Best wishes,
Kirk
The LearnEnglish Team

Soumis par Adediran le mar 20/10/2015 - 07:13

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Please, can someone tell me which one of these is correct: 1) May John keep doing the task.... or 2) May John keeps doing the task...

The first sentence is correct, though it is not a particularly natural or likely sentence.

After modal verbs such as 'may' we use the base form of the verb, without the third-person 's'.

Best wishes,

Peter

The LearnEnglish Team

Soumis par habib047 le lun 19/10/2015 - 20:52

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can anyone please explain the rules of having . I mean which one will be right I am doing fun I am having fun

Hello habib047,

I'd encourage you to look up 'fun' in the dictionary – see the Search box on the lower right. 'do' does not collocate (go with) 'fun', but 'have fun' is a common phrase, as you'll see in the dictionary.

Best wishes,
Kirk
The LearnEnglish Team

Soumis par rewand le dim 27/09/2015 - 17:26

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Hello teachers. I have a question for you if you don't mind. Please can someone say why in this sentence the 'would' instead of 'would have'? I thought back to our childhood, when she and I would find ourselves walking ...

Hello rewand,

This is 'would' used to describe past habits. For example, I could say 'When I was a child, I would go for long walks every morning'.

'Would have' here would describe an unreal past - something the speaker would have done (if it had been possible).

Best wishes,

Peter

The LearnEnglish Team

Soumis par praixx le ven 11/09/2015 - 14:51

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Here is two confusing sentence... 1. If we don’t hurry we could be late. >>>Here could be is used to shows something is possible in future. but, 2. It could be very cold in winter. >>>Here could be is used to describe past. how??

Hello praixx,

In 2, 'could be' seems to be expressing a possible future, just as it did in 1.

Best wishes,
Kirk
The LearnEnglish Team

Soumis par elena24 le mar 09/06/2015 - 14:45

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Hello, I'm a little confused about some forms of modal verbs: you say that we use the negative "couldn't" to show that something was impossible, however, some books say that for impossibility in the past we should use "can't have" or "couldn't have" (for ex. Sarah hasn't contacted me. She can't have got my message.) So, where's the truth? Thank you a lot

Soumis par Peter M. le mar 09/06/2015 - 22:45

En réponse à par elena24

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Hello elena24,

You are confusing two different uses here. The first is the modal 'couldn't', which can describe past impossibility:

He couldn't swim when he was six.

I couldn't stop playing the game.

We cannot substitute 'can't have' here.

The second form is the perfect modal 'can't have', which is used when we are deducing somether from evidence. It shows our belief or inference about a situation, not a fact about the past. For example, in your sentence above the speaking is deducing that Sarah can't have got the message because she has not been in touch - a logical deduction from evidence. In this use both 'couldn't have' and 'can't have' are possible.

Best wishes,

Peter

The LearnEnglish Team

Soumis par meena1234 le mer 13/05/2015 - 11:52

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which modal should be used in the following statement? Please give reasons as well You_____ do your work properly. i think so it should be 'should'

Hello meena1234,

Almost any modal verb can be used in this sentence: will, can, should, could, might, may, won't, can't, must etc. Without a context it is impossible to say which is needed.

Best wishes,

Peter

The LearnEnglish Team

Soumis par DavideV le mar 05/05/2015 - 15:01

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Good morning! Reading this article, I find myself a little surprised as I always assumed a different pattern of usage for "may", "might" and "might have" because I basically would tend to think about how a sentence sounds more than how much it adheres to grammar rules. I know it's a bad, bad habit and that's why I tend to come to the basics from time to time, although being in the upper-intermediate/advanced level. This is most likely a wrong mindset coming from (another) bad habit of trying to search a direct translation of tenses between my native language and English so a big THANK YOU for this great article.

Soumis par abdullah rajab le jeu 19/03/2015 - 14:58

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Hey there so I'd like asking what is the difference between those sentencesq could be very cold in winter. It can be very cold in winter. and please point out any mistakes in the question text thanks.

Soumis par Knightrider le sam 17/01/2015 - 14:06

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Hello, I need your help in understanding the difference between "must" and "will" when we want to express a deduction. What's the difference between them? Is one stronger than the other? Are they used to express different nuances? For example: The phone's ringing. That must be Dad...or that'll be dad? Thank you for your insights.

Soumis par Peter M. le dim 18/01/2015 - 11:12

En réponse à par Knightrider

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Hello Knightrider,

The difference is quite subtle. We generally use 'must' when we are making a logical deduction which has a strong basis. For example, we would say 'That must be Dad' if we had been waiting for a phone call from Dad for a while and it was overdue. We would use 'will', on the other hand, for something that is normal, expected or typical. For example, we would say 'That will be Dad' if the phone rings and we know that Dad always phones at this time on this day. In other words, 'must' expresses a logical deduction based on some kind of evidence, whereas 'will' expresses an expectation based on the normal pattern of things.

Of course, these are subjective assessments rather than objective rules of what is correct and what is incorrect. This means that a given speaker can choose which form is most appropriate for a given situation, depending on how they see that situation.

I hope that helps to clarify it for you.

Best wishes,

Peter

The LearnEnglish Team

Soumis par Apurva Shah le mer 22/10/2014 - 14:28

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if we are talk about the past..- It is nearly eleven o'clock. They should have arrived by now, is right -or- It was nearly eleven o'clock. they should have arrived by now??

Hello Apurva Shah,

If you are speaking of the past, in most contexts you would say 'It was nearly eleven o'clock'. But please note that 'by now' doesn't work in the past, as 'now' refers to the present. Therefore the end of your sentence should be something like 'They should have arrived by then (or: 'by that time')'.

Best wishes,
Kirk
The LearnEnglish Team

Soumis par imran_000 le jeu 02/10/2014 - 07:41

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if i am not certain about a past event 1.Then which one should i use could have+pp or might have+pp or may have+pp 2.or all mean same and can be used interchangeably. please explain in the light of the above examples that you have used above It’s ten o’clock. They might have arrived now. They could have arrived hours ago. they may have arrived by now

Hi imran_000,

In the specific context you mention, all three modal verbs structures you list mean the same thing - they can be used interchangeably.

Best wishes,
Kirk
The LearnEnglish Team

Soumis par cabronasoon le mer 25/06/2014 - 02:59

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Can I use couldn't for possibility in the second conditional sentence? For example, If I lived in a big city, I couldn't breathe fresh air every morning.

Hello cabronasoon,

Yes, it's perfectly fine to use 'could' in this way.

Best wishes,

Peter

The LearnEnglish Team

HI Can i write like this? IF i lived in a big city, i wouldn't breathe fresh air every morning... Thank you

Soumis par Kirk le mer 19/11/2014 - 06:43

En réponse à par bharathviki

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Hello bharathviki,

Yes, that sentence is grammatically correct.

Best wishes,
Kirk
The LearnEnglish Team

Sir, Can I also say : If I lived in a big city, I may not breathe fresh air. Or will I have to use 'might' in place of 'may'

Soumis par Peter M. le sam 28/09/2019 - 08:43

En réponse à par dipakrgandhi

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Hello dipakrgandhi,

I think the best option here would be 'would'. This is not choice you make or a possibility, but a certain consequence, provided the condition is fulfilled.

Peter

The LearnEnglish Team

Soumis par Baloch Faisal le mar 25/03/2014 - 12:08

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Sir Peter, whether the meaning of "could" and "Perhaps/Maybe" is same, according to this ? If we don’t hurry we could be late. (= Perhaps/Maybe we will be late).

Soumis par Peter M. le mer 26/03/2014 - 08:46

En réponse à par Baloch Faisal

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Hello Baloch Faisal,

Yes, that is a reasonable approximation of the meaning.

Best wishes,

Peter

The LearnEnglish Team

Hi Baloch Faisal,

I wouldn't say that could and perhaps or maybe have the same meaning, as they are used differently in a sentence (could is a modal verb), but it's true that all of them are used to indicate possibility. In this way, yes, "we could be late" and "perhaps we will be late" essentially mean the same thing. As Peter and I point out in response to your other question, many speakers would say "we might be late" in this situation.

Best wishes,

Kirk
The LearnEnglish Team

Soumis par Muhammad Anisu… le mar 03/09/2013 - 11:35

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Hello,

I can't get meaning of following sentences-

We knew it could not be true.
He was obviously joking. He could not be serious.

Thanks a lot

Anis

'Could not' in these sentences refers to something being not possible.  Therefore we can rephrase each sentence as follows:

We knew it could not be true.

We knew that it was definitely not true.

He was obviously joking. He could not be serious.

It was not possible that he was being serious.

I hope that clarifies it for you.

Best wishes,

Peter

The LearnEnglish Team

Soumis par aymen.omg le mer 19/06/2013 - 18:18

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I'm very confused about modal verbs , I don't know how to choose the proper one

It is very confused subject .

Soumis par yantisukadi le lun 06/05/2013 - 04:55

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Hello everyone...

I'm newcomer here. I hope I can improve my english by joining this site. I'd like to make friend too... ^_^

Soumis par arihat le dim 05/05/2013 - 10:01

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hi

i'm  new member please any body  could me?

Soumis par dg7 le sam 04/05/2013 - 07:51

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Hello, and thank you for your great grammar service.

I am confused by these examples:

It could be very cold in winter. (= Sometimes it was very cold in winter.)
You could lose your way in the dark. (= People often lost their way in the dark)

I thought that "could" is used for conditionals. I mean that what I read above is that every winter can be very cold (not just in the past), and that I can lose my way in the dark even in the future. Am I totally wrong?

Regards.

Daniele Giacomini

Hello dg7!

These sentences are both past. For example, in Europe in the 17th and 18th century, there was a "mini ice age" when the weather was unusually cold.

Back then, it could be very cold in winter.

Likewise, for the second sentence:

In the past, there were no electric street lights. You could lose your way in the dark.

That's all - it's difficult to understand without the context of the sentences, but you can use this structure to talk about the past.

Regards

Jeremy Bee

The LearnEnglish Team

Soumis par Farrukh Rashee… le mer 20/03/2013 - 07:19

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Hi! well my question is this, Can we use Must not instead of Can not or Could Not

for impossible actions.

Hello Farrukh!

Grammatically, you can, but mustn't with this meaning is uncommon these days. Generally, we use can't.

Hope that helps!

Regards

Jeremy Bee

The LearnEnglish Team