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

Submitted by Alaul Mechanical on Fri, 27/10/2017 - 14:54

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If we don’t hurry we could be late. why we use be with could? as per Learn English We use the modals could, might and may to show that something is possible in the future, but not certain

Hello Alaul Mechanical,

As the explanation says, 'we use the modals could, might and may to show that something is possible in the future, but not certain'.

If we don't hurry we could be late.

Here, it is not certain that we will be late but it is possible. You could replace 'could' here with 'might' or 'may'

If we don't hurry we might be late.

If we don't hurry we may be late.

 

If we use 'will' here then the meaning changes:

If we don't hurry we will be late.

Now the speaker is sure that they will not be on time if they do not hurry. There is no doubt or uncertainty; it is certain and not just possible.

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by Ali Sahir on Mon, 11/09/2017 - 06:54

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sir please explain "must+be+ing" with some examples in the context.

Hello Ali Sahir,

I'm afraid we can't provide long explanations like this in the comments sections. 'Must' has many uses. If you have an example which you have found which you would like us to explain or comment on then please post that in a reply and we'll be happy to answer.

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by jitu_jaga on Sun, 20/08/2017 - 20:04

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sir, we can write ' it may/might/could rain tomorrow.' but is it right to say ' it would rain tomorrow.' can we use 'would' for future possibility? please answer..

Hello jitu_jaga,

'Would' is not used for future possibility without some kind of condition: Knowing out luck, it would rain tomorrow if we went to the beach. 

We do not use 'would' for future possibility in other cases, however.

 

Best wishes,

Peter

The LearnEnglish Team 

Submitted by Seyyed on Sun, 06/08/2017 - 13:39

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Hello, I am Wondering whether one can use sentences like "It could/may/might have not happened"? Or " It could not/may not/might not have happened"? for negation of possibilities in the past, which also are possibilities and not happened? Thanks in advance

Submitted by Peter M. on Tue, 08/08/2017 - 07:40

In reply to by Seyyed

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Hello Seyyed,

The negation can be put in either position with no change in the meaning:

She might/may not have seen him.

She might/may have not seen him.

Both these sentences mean it is possible that she did not see him.

 

Note that 'could' is different. Here the position of the negation changes the meaning:

She could not have seen him. [is is impossible that she saw him]

She might/may have not seen him. [it is possible that she did not see him - the same meaning as above]

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by SonuKumar on Mon, 24/07/2017 - 06:39

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Sir, I think He must be sleeping, It's for present, But for past, Should I use this- I thought He must have been sleeping yesterday ?

Hello SonuKumar,

I'd probably just say 'I thought he was sleeping'. 'I thought' already indicates supposition. Or you could just say 'He must have been sleeping', which indicates supposition. The two forms together would mean you are emphasising the act of making a supposition about him sleeping.

All the best,
Kirk
The LearnEnglish Team

Submitted by SonuKumar on Sun, 16/07/2017 - 06:46

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what are the usages of 'Must, must be, and must have been' please help me understand with at least one example for each ?

Submitted by sumanasc on Sat, 01/07/2017 - 17:33

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Hi Kirk Thank you for answering my previous question . Please I have one more query. I would go to the cinema , if I have the time. Is the above sentence correct or should I say I would go to the cinema if I had the time. Many thanks for your help

Submitted by Peter M. on Sun, 02/07/2017 - 07:25

In reply to by sumanasc

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Hello sumanasc,

We would use 'had' here. Conditional forms are either about likely/possible events or unlikely/impossible events and we do not mix the two in one sentence. Therefore in your sentence we would either use 'will... have' (likely) or 'would... had' (unlikely).

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by sumanasc on Sat, 01/07/2017 - 13:34

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Hi Kirk Can you please tell me whether the sentence under modal verb " I could help you , if I find my car " is correct . Many thanks

Submitted by Kirk on Sat, 01/07/2017 - 15:07

In reply to by sumanasc

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Hello sumanasc,

You could probably hear some people say 'I could help you if I find my car', or perhaps find it in writing, but the grammar is a little bit non-standard. This is because the sentence has one verb ('find') in a first conditional structure and the other verb ('could') in a second conditional structure. Please take a look at our Conditionals 1 page to see what I mean.

The sentence in full first conditional structure would be 'I can help you if I find my car' and in full second conditional structure would be 'I could help you if I found my car'.

All the best,
Kirk
The LearnEnglish Team

Submitted by khuder on Wed, 21/06/2017 - 03:23

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Hi there, I have always tried to learn Modals but I find them really difficult! We use could have to talk about possibility and about ability. They could have arrived hours ago( did they arrived or not?) They could have killed him.( did they kill him or not?) you said we use could have to talk about something was possible at some time but didn't happen. How can we know if this happened or maybe happened? thanks to the all team members

Hello khuder,

Modals have lots of different uses, so it's best to take them in small doses! 'could have' implies that the possibility existed but was not realised, so, for example, in your two examples, they did not arrive hours ago and they did not kill him. If you want to make it clear that something was possible and did happen, most of the time you'd probably just use a past simple form, e.g. 'they arrived hours ago', 'they killed him'.

All the best,
Kirk
The LearnEnglish Team

Khuder, I'm from Brazil and I'm not 100% sure about what I'll tell you now, but, in my opinion, you need to learn how to use only the modal "Could", as soon as you learn it, you will be able to use it with "have" cause it will sound clearer for you. In your example "They could have arrived", it might be more difficult if you analyse it out of a context for example. Oh, they could have arrived many hours ago, lets prepare something to them... So in this case they "maybe yes/not have arrived many hours ago, it's a possibility but you prefer to prepare something to them... They could have killed him... Is not 100% of sure that they killed him, maybe yes maybe not, it will rely on an investigation... I don't know if I helped you but I tried. Thanks Bye bye.

Submitted by kiranpn on Wed, 14/06/2017 - 04:57

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Hi there, I'm always baffled by the 'would'. how to differentiate that would in the sentence is conditional or talking about the possibility ( like might or could )?. Do we need to consider the whole context to differentiate between these two? for instance, this paragraph is talking about the Computer Networking terminology. " Data link layer protocols add a trailer to the end of each frame. The trailer is used to determine if the frame arrived without error. This process is called error detection and is accomplished by placing a logical or mathematical summary of the bits that comprise the frame in the trailer. Error detection is added at the data link layer because the signals on the media could be subject to interference, distortion, or loss that would substantially change the bit values that those signals represent." It would be great if you could help me on this regard. Regards, Kiran

Namaste Kiran,

'would' and all of the different modal verbs can indeed be difficult to learn to use, as they all have multiple uses is different contexts. 'would' is not used to talk about possibilities in the same way as 'may' and 'might'; rather, it communicates the idea of something unreal (e.g. because it's hypothetical or imaginary).

We don't normally comment on texts from other sources, but I'll try to help you with this one since it's very specific. In the fourth sentence, the 'because' clause is talking about a hypothetical situation, more specifically a situation in which the signal is subject to interference. Since this signal interference situation is hypothetical, the changes in the bit values that would result because of it are also hypothetical. The hypothetical nature of this signaled by 'would'. If we said 'will', it implies more reality than is appropriate for this situation.

Does that help?

All the best,
Kirk
The LearnEnglish Team
 

Submitted by Knightrider on Mon, 05/06/2017 - 22:02

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Hello, I've come across the phrase "I wouldn't know" and looking it up I' ve found out that it can mean two things: 1)I couldn't say, when you haven't experienced something 2) How am I supposed to know?, when you are not the right person to answer a question/comment. Is that correct? Thank you.

Submitted by Peter M. on Tue, 06/06/2017 - 06:55

In reply to by Knightrider

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Hello Knightrider,

I think that's a good summary. The communicative meaning of the phrase is very much dependent on the context, so it's important to look at how it is used in context, not in isolation.

 

Best wishes,

Peter

The LearnEnglish Team

Hello Peter, Yes absolutely. Context is all-important to distinguish the two meanings. I just wanted to be sure that I have grasped both senses. Thanks again Regards.

Submitted by girlbah on Sat, 27/05/2017 - 00:46

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Hi! How can you differentiate between ability, possibility, probability and obligation in the sentence below? ´´Every person has particular ways to do things that may seem strange to others´´. Thank you!

Submitted by Kirk on Sat, 27/05/2017 - 06:25

In reply to by girlbah

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Hello girlbah,

One way you could do it is by using other words or phrases instead of 'may'. For example, 'be able to' for ability, 'it is possible' for possibility, 'it is likely' for probability and 'must' or 'should' for obligation.

Which one makes the most sense to you here?

All the best,
Kirk
The LearnEnglish Team

Submitted by Wolframio on Mon, 24/04/2017 - 18:49

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Whats the meanning of "vicious dog"? Thanks

Hello Wolframio,

The phrase is 'a pretty vicious dog'. 'Pretty' here means 'quite' or 'fairly'.

You can find the meaning of 'vicious' in any online dictionary - see here, for example.

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by mgfielrocha on Fri, 17/03/2017 - 10:33

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Good day ! what tense is `must have been´ ?

Hello mgfielrocha,

In 'must have been', 'have been' is a perfect infinitive, which in this case is used to speak about the past, but as far as I know there is no name for the tense in this form. This is because 'must' and most modals don't really have tenses -- we have to use other words to express the same idea in a different time. For example, to speak about past obligation, we have to use 'had to' instead of 'must'.

If you're interested in learning more about this, the Wikipedia English modal verbs page would be a good place to start.

All the best,
Kirk
The LearnEnglish Team

Submitted by judeee on Fri, 17/03/2017 - 05:57

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Hi sir, can we use 'could' to make a statement in the future? E.g; I could have been driving home before she arrives on Monday.

Hi judeee,

You can use 'could' with future reference, but not 'could have'.

 

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by duffyzee on Fri, 23/12/2016 - 23:55

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Dear admin, Is it grammatically correct to write " May your happiness will never last " ?

Hello duffyzee,

I'm afraid that sentence is not grammatically correct. The problem is that you can't use two modal verbs ('may' and 'will') together in this way. Perhaps you mean 'may your happiness never last'? Or 'may your happiness never end'?

All the best,
Kirk
The LearnEnglish Team

Submitted by Diya on Sat, 26/11/2016 - 00:15

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Dear the English learner team Could you please explain what are the differences between these sentences. and what are the role of the verbs (has to, might, if + will and either+have to) as I always make mistake when I use these verbs. Thank you 1. Ali has to wake up at 8:00 am tomorrow. 2. If Ali wakes up late tomorrow, he might miss the train. 3. if it rains on Friday, the party will be cancelled. 4. Either the party will be cancelled, or they have to move it indoors.

Hello Diya,

It would take quite a long time to answer all of your questions thoroughly! To start with, I'm going to suggest some pages that I think will help you. After you've read through them, if you'd like to ask us a specific question, please let us know.

First of all, you can learn about 'have to' on our Modals 1 page. Our Conditionals 1 and 2 pages explain sentences that begin with 'if'. Finally, for 'either ... or', I'd recommend the Cambridge Dictionary's page on this topic.

All the best,
Kirk
The LearnEnglish Team

Submitted by heeppee creepy on Wed, 31/08/2016 - 01:19

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I can see nobody is interested in answering my question. Since every question I see on this page has been answered the same day and almost in a few hours, I have to assume that either my question makes no sense at all as to be analysed or I accidentally broke any of the rules on this page. Please, let me know if the latter is the reason why no answer has been replied. Thanks.

Hello Heeppee creepy,

Our role here is to maintain the site and add to it. Answering questions in the comments section is something which we do in addition to that, when time allows.

We see many comments every day and we make decisions on which comments to answer first. Comments which reveal problem with the site have priority. After that we look at which comments are precise, concise and can be answered quickly, so that we can help as many people as possible in the limited time we have. Questions which are long, hard to read and contain multiple queries, such as yours, take a long time for us to answer. If you had asked one concrete question then you would receive an answer quickly. Instead you asked multiple questions in one block of text, making it hard to read.

We will answer you but you must be patient when you ask such a long question.

 

LearnEnglish is a free service and our team is a small one. If the time taken to respond to your comment is too long for you then there are many paid services which will provide you with a quicker response, I am sure.

 

Best wishes,

Peter

The LearnEnglish Team

No, its OK. I just thought nobody had noticed my question or I had broke a rule on the site, but now I know that I'm "on the air" and that's enough to me. I apologise for the type of question I asked. I know I'm not very concise most of times.

Submitted by heeppee creepy on Sun, 28/08/2016 - 07:50

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Hi all, I 'm new here and I would like to ask a question to the experts. I prefer to study modal verbs one by one, until I really get to master the one I'm studying I keep going with the next one , and by now I'm stuck with SHOULD +HAVE. firstly I'd like to know if these sentences are OK: 1 it's only ten and she gets off work at 11, she shouldn't have left her office yet, I'll ring her. 2 it's ten and she starts working at nine, she should have arrived at her office by now, I'll ring her ! 3 it's 1 o'clock and she doesn't answer, she shouldn't have arrived at her office yet , I 'll call her later. In the third sentence is where I have serious doubt, first sentence has a positive connotation since I'm happy because I think I still can get a hold of her , and in the third sentence the connotation is negative because I feel worry about the fact that I might not be able to reach her because she hasn't arrive.. The same as in : 1 Tom is very happy, his wife should've told him about her pregnancy already . 2 Tom is very happy, his wife shouldn't have told him about her plans of abortion yet. I'd like to know if SHOULDN'T HAVE can be used with this connotation, and what would the change be if I leave out the ALREADY, YET, And BY NOW of these sentences . please correct my sentences cause this is what I'm here for ! Thanks .

Hello Heeppee creepy,

In answer to your questions:

it's only ten and she gets off work at 11, she shouldn't have left her office yet, I'll ring her.

'Shouldn't' is possible here, though 'won't' is perhaps more likelyt if your intention is to make a guess about what is likely.

 

it's ten and she starts working at nine, she should have arrived at her office by now, I'll ring her !

Again, the same comment applies. 'Should' is possible here.

 

3 it's 1 o'clock and she doesn't answer, she shouldn't have arrived at her office yet , I 'll call her later.

Here 'shouldn't' suggests a value judgement - that it would be wrong for her to do this. A better alternative is 'won't', which is neutral in terms of judgement and describes simply the speaker's expectation/belief.

1 Tom is very happy, his wife should've told him about her pregnancy already .

2 Tom is very happy, his wife shouldn't have told him about her plans of abortion yet.

Neither of these sentences are likely. Using 'should' in this way suggests a value judgement on the behaviour of Tom's wife - that it was wrong to withhold or give the information, and it does not fit with what I guess is your intended meaning. I suspect the meaning you have in mind would be best expressed by 'must have' and 'mustn't have' respectively - these are modal verbs used to make logical deductions or inferences on the basis of observed evidence.

We don't correct posts by users on LearnEnglish, I'm afraid. We simply have too many users to do so, and as this is a site provided free of charge we have only a small team of people working on it. It is not possible for us to provide a correction service.

I hope the above clarifies these issues for you.

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by pyramid on Sun, 31/07/2016 - 12:35

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It had better be. How to make ∆∆∆ Negative__Yes/no question__Wh question

Submitted by frisky on Fri, 29/07/2016 - 11:36

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Excuse me sir, I watched a movie and there's a conversation that baffle me. "I wondered when I'd be seeing you, Mr. Potter" does it the same like : "I wondered when I'd see you, Mr. Potter" If these sentences don't have the same meaning, what is the intention of both sentences ? Thank you very much :)

Hello frisky,

In this context both forms have a very similar meaning.

 

 

Best wishes,

Peter

The LearnEnglish Team

Submitted by Vijay Soni on Thu, 07/04/2016 - 19:50

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Hello sirs!! Please accept my warm regards on doing such a wonder job. I am confused over using "May" and "Might" and I appreciate, If I am known the difference of using "May" and "Might". Thank you sir!!

Hello Vijay Soni,

There is little difference  when talking about probability, but please remember that modal verbs have many meanings, so 'may' can also be used for permission, for example. We have organised this section (on modal verbs) so you can see which different modals are used for each concept.

There are differences in meaning when the perfect forms (may have vs might have) are used, but the single-word forms are essentially interchangeable.

 

Best wishes,

Peter

The LearnEnglish Team