'can' and 'could'

Level: beginner

Possibility and impossibility

We use could to show that something is possible, but not certain:

They could come by car. (= Maybe they will come by car.)
They could be at home. (= Maybe they are at home.)

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.)

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 could have to make guesses about the past:

It's ten o'clock. They could 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.)

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.

Ability

Level: beginner

We use can and can't to talk about someone's skill or general abilities:

She can speak several languages.
He can swim like a fish.
They can't dance very well.

We use can and can't to talk about the ability to do something at a specific time in the present or future:

I can see you.
Help! I can't breathe.

We use could and couldn't to talk about the past:

She could speak several languages.
They couldn't dance very well.

Level: intermediate

We use could have to say that someone had the ability or opportunity to do something, but did not do it:

She could have learned Swahili, but she didn't want to.
I could have danced all night. [but I didn't]

Permission

Level: beginner

We use can to ask for permission to do something:

Can I ask a question, please?
Can we go home now?

could is more formal and polite than can:

Could I ask a question please?
Could we go home now?

We use can to give permission:

You can go home now.
You can borrow my pen if you like.

We use can to say that someone has permission to do something:

We can go out whenever we want.
Students can travel for free.

We use can't to refuse permission or say that someone does not have permission:

You can't go home yet.
Students can't travel for free.

Requests

We use could you … as a polite way of telling or asking someone to do something:

Could you take a message, please?
Could I have my bill, please?

can is less polite:

Can you take a message, please?

Offers

We use can I … to make offers:

Can I help you?
Can I do that for you?

We sometimes say I can ... or I could ... to make an offer:

I can do that for you if you like.
I could give you a lift to the station.

Suggestions

We use could to make suggestions:

We could meet at the weekend.
You could eat out tonight.

Questions and negatives

We make questions by putting the subject after can/could:

Can I ...?
Could I ...?
etc.
Can you ...?
Could you ...?

 

The negative form is can't in spoken English and cannot in written English.

We sometimes say cannot, but it is very emphatic.

The negative form of could is couldn't in spoken English and could not in written English.

can and could: possibility 1

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can and could: possibility 2

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can and could: other uses 1

Matching_MTYzNjk=

can and could: other uses 2

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Everything's clear now, Peter. You've been most helpful. Thank you. Regards.

Submitted by Danielle N on Fri, 20/06/2014 - 07:12

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Hello, May I know whether the use of "could" in the following sentence is correct? "Go and ask him whether he could differentiate the two." If incorrect, could you please advise me the correct way to say it? Thank you.

Submitted by Peter M. on Sat, 21/06/2014 - 10:29

In reply to by Danielle N

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Hello Pocoyo,

That sentence is correct.  You could also use 'can' in the sentence, with a different meaning: 'could' implies a hypothetical situation in the sense that the person will not have to do it, and your question is purely speculative, while 'can' implies a real situation and that you want the person to try to differentiate between the two items for you.

Best wishes,

 

Peter

The LearnEnglish Team 

Hello Peter, Thank you very much for your explanation! : )

Submitted by chatterjee on Tue, 10/06/2014 - 11:33

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there can be storm there could be storm the second one is used for uncertain situations.You said that can is used for possible situations..and the meaning of possible is "that may exist or happen, but that is not certain". So that means both can and could expresses possibility...So wats the difference between these two above sentences ???

Hello chatterjee,

The difference between "There can be storms" and "There could be a storm" is that the first sentence is talking in general about the climate in a place. For example, on Mt. Everest, there can be storms (at any time of the year). Here the sentence is about the climate there in general.

"There could be a storm" would be used to refer to a specific occasion. For example, if you're planning a trek to the Mt. Everest base camp and are thinking about what gear to take, you might want to take raingear as "there could be a storm" while you are on your trek. Here you're talking about a specific trek, not the climate in general.

As you can see, there is not really a difference in meaning here - it's more a question of use. I hope this helps you.

Best wishes,
Kirk
The LearnEnglish Team

Submitted by chatterjee on Mon, 09/06/2014 - 20:40

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sir as you said that can is used for general statements which are possible..Does this mean that "can" is used for showing 100 % surety.. For example - Using mobile phones while driving can be dangerous...Does this means that using mobile phones might be dangerous (more that 50% dangerous) or does that mean it is 100 % dangerous..?? As you said that can and could both are used to express possibility and could is used for uncertain...So does can expresses definite situations (100% possibility) or does it expresses a situation which is very likely to get happened (more possible than could but not 100% ) ??? i googled the meaning of possible and found that possible means "that may exist or happen, but that is not certain or probable." So possible in itself means uncertain..so why can is not used for uncertain situations... Can i say that can expresses more possibility than could but not 100 % possibility. For example - 1) There could be a storm later. (30-40 % possibility) 2) smoking can cause cancer. (70 % possibility but not 100 %) Conclusion - can expresses more possibility compared to could but it does not expresses 100% possibility....Am i right ???

Hello chatterjee,

When can is used to make a general statement like this, the focus is on what is possible, not how probable it is. To talk about probability or possibility in a more specific context, could, may or might are generally used.

I'd recommend that you pay attention to how can and could are used in context, i.e. in written texts and in conversations (see our Magazine for lots of articles), because you can get a much better sense of their meaning when there is some kind of meaningful context. These grammar exercises are meant to give you a start and to help you understand some of the finer points but the real test is to understand them in use in oral or written texts. Both can and could are used extensively, so almost anything you read will have examples of them.

Best wishes,
Kirk
The LearnEnglish Team

Submitted by Baloch Faisal on Wed, 26/03/2014 - 12:03

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Hi Sir Peter and Sir Kirk, how can i get command over the using of "can" and "could", still confusion exists regarding this, any advise plz share.

Submitted by Learner S on Tue, 25/03/2014 - 20:33

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Hi sir 1. John could be the one who stole the money. 2. John could have been the one who stole the money. 3. John could go to jail for stealing the money. All these sentences denoting possibility....first sentence denote present possibility 2nd past and 3rd future.........In first sentence there is past form of verb(stole) instead of base form.....Why?Though the sentence is denoting present state and we r giving an opinion......... Q=1. If I had more time, I could travel around the world. 2. If I had had more time, I could have traveled around the world. 3. If I had more time this winter, I could travel around the world. All these sentences also denoting possibilities...........i couldn't make any difference between them.............

Submitted by Peter M. on Wed, 26/03/2014 - 08:20

In reply to by Learner S

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Hello Learner S,

The verb 'stole' is a past form because it describes past time - the stealing took place in the past.  We have an opinion now ('could be') about someone who did something in the past.

In your second set of sentences you have different time references:

1 - hypothetical present

2 - hypothetical past

3 - hypothetical future

I hope that helps to clarify it for you.

Best wishes,

 

Peter

The LearnEnglish Team

Thanks sir this elaboration really helped me a lot.........

Submitted by er555 on Tue, 25/03/2014 - 11:19

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Hi, for future possibility, we should say "This could be you." to indicate an aspiration especially when it's referred to a specific picture or person description. But if we say "This can be you.", will it increase the possibility, ie, it's no longer a future possibility and it's very likely, it's real? Would love to hear your comments. Thanks.

Hi er555,

I'm not sure I'd say could indicates an aspiration here - it's more that the possibility exists, and there is a sense that it depends on some unnamed conditions (e.g. "if you exercised every day").

Changing could to can would indeed indicate that the possibility is greater - perhaps the condition would be "if you exercise more". This is not a reality, but by using the present simple (you exercise), the condition is regarded as being more likely.

Best wishes,

Kirk
The LearnEnglish Team

Submitted by Baloch Faisal on Mon, 24/03/2014 - 11:38

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hi sir, i want to know difference between both following statements, (1) If we don’t hurry we could be late. (2) If we don’t hurry we can be late.

Submitted by Peter M. on Tue, 25/03/2014 - 09:42

In reply to by Baloch Faisal

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Hi Baloch Faisal,

We would rarely if ever use the second sentence in English.  This is because the sentence is referring to something in the future which is possible but not certain and for this meaning we use the modal verbs could, may or might.  You can learn more about this here.  Can is used to talk about in more general terms about what is possible, as you can see from the explanation at the top of this page.

I hope that helps to clarify it for you.

Best wishes,

 

Peter

The LearnEnglish Team

Hi Baloch Faisal,

Yes, I would say that it is incorrect. Perhaps there is some unusual situation in which it might work, but I can't think of one. As Peter says, it would be far more normal to use might, may or could instead of can here.

Best wishes,

Kirk
The LearnEnglish Team

Submitted by Orionne on Wed, 19/02/2014 - 11:06

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Hi! I'd like to ask if "I can imagine how varieties of sarcasms WOULD be preponderant on existing social networking sites in replacement of vulgar remarks and nasty comments." is correct. I have doubts though. Thank you.

Hi Orionne,

It's not an entirely correct sentence, I'm afraid.  I think a better version, trying to keep as close to your version as possible, would be something like:

I can imagine how various kinds of sarcasm WOULD be preponderant on existing social networking sites in place of vulgar remarks and nasty comments.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by Coldfan on Thu, 30/01/2014 - 06:11

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Hello, I have a question about impossibility in the past:

We use the negative can’t or cannot to show that something is impossible.We use couldn’t/could not to talk about the past:

He was obviously joking. He could not be serious.

What if I say: "He was obviously joking. He couldn't have been serious". What is the difference between "he couldn't be serious" and "he couldn't have been serious" if we are talking about impossibility in the past? To me "couldn't be" in the sentence "He was obviously joking. He could not be serious" seems like he tried, but failed to be serious (ability during a specific event) or something like "he couldn't be serious when he was a little baby" (impossibility in general).

Hello Coldfan,

In this context I would say that the two forms are intechangeable:

He was obviously joking. He couldn't be serious.

He was obviously joking. He couldn't have been serious.

However, there is a difference in terms of range of meaning.  We can use 'could' for both general and specific ability in the past.  For example:

He couldn't swim. [general ability - he didn't know how]

He couldn't swim because he was tired. [specific ability in a particular case]

However, we can only use 'couldn't have' for particular situations, not general ability.

I hope that helps to clarify it for you.

Best wishes,

 

Peter

The LearnEnglish Team

Thanks for the reply, Peter.

As far as I understood, the sentence "He was obviously joking. He couldn't be serious" may mean that he didn't have the specific ability in a particular situation. For example, he was trying to be serious, but failed though. On the other hand, the lack of the general ability of being serious is also possible. For example, he was born like this.

Am I right?

 

Hello Coldfan,

Yes, that's correct, though I think the idea that somebody is born without the ability to be not serious is fairly unlikely!  Therefore, though 'couldn't' can be used for general and specific ability, the context of the sentence make is clear that the speaker is almost certainly talking about a specific situation rather than a general inability.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by krishna0891 on Sat, 11/01/2014 - 10:17

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Sir,

I have come to know that we use can and could also for the possibility (mostly we use may or might).

Ex:- Interviewer to Candidate: You could go now.

My question is that while we are talking about possibility, when do we need to use may, might, can, could, would?

please explain with some examples......

Thanks and Regards

KRISHNA

Submitted by Peter M. on Sun, 12/01/2014 - 09:56

In reply to by krishna0891

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Hello Krishna,

That's quite a detailed question, with five different modals in one go!  Fortunately, we've got just the page you need, which looks at how we use modal verbs to talk about things that are certain, probably and possible, gives examples and explanations, and also provides an exercise to practise them.  You can find the page here.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by sanover on Mon, 06/01/2014 - 09:41

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Hi Team,

Is it possible to use "did i anything wrong" because usually we use it as "did i do anything wrong".

Could you please help me on this.

Thank you 

Submitted by Peter M. on Mon, 06/01/2014 - 12:39

In reply to by sanover

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Hello sanover,

To form the question it is necessary to use the auxiliary verb, so 'Did I do...?' is the correct form.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by sanover on Thu, 02/01/2014 - 10:44

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Hi Team,

I'm really surprised to see this kind of an active helpful site :) Hats off to the Team behind this org.

And this is my doubt, what is the actual meaning of "One of a kind"?

Is it mean like there is nothing like this kind or these all are the same kind.

Could you please help me on this.

Thank you

Submitted by AdamJK on Thu, 02/01/2014 - 11:15

In reply to by sanover

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Hi Sanover,

Thanks for your compliment - we appreciate it! If you enter 'one of a kind' into the 'Cambridge Dictionaries Online' box at the right-hand side of the page, you should see the answer to your question.

Best wishes,

Adam

The LearnEnglish Team

 

Hi Adam,

Yeah :) Thanks alot for your prompt reply.

Thank you.

Submitted by EnglishIsFun2013 on Mon, 16/12/2013 - 04:12

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Hi Sir,

Please clarify about the different between 'Why can we ...?' and 'Why we can...?'

Thank you.

Submitted by Peter M. on Mon, 16/12/2013 - 22:23

In reply to by EnglishIsFun2013

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Hi,'Why can we...?' is the normal word order for questions:'Why can we have a free day on Saturday, but not on Monday?'

'Why we can...?' does not seem a correct alternative to me.  It could appear in an indirect question such as 'Can you tell me why we can...?', but not by itself.

I hope that answers your question.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by kamrina on Thu, 07/11/2013 - 23:28

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which one is correct? we can celebrate our birthdays together? or we could celebrate our birthdays together? please reply asap

Hi kamrina,

Are these sentences supposed to be questions? If so, they should be:

Can we celebrate our birthdays together?
Could we celebrate our birthdays together?

Both of these questions are correctly formed. The one with could is more polite or formal than the one with can, but they have the same meaning.

Best wishes,

Kirk
The LearnEnglish Team

and also, for eg if some-one suggests something to me. so should my reply be "yeah I can do that" OR "yeah I could do that"

Hello kamrina,

Both are possible.  'Can' makes it sound like the possibility is much more likely, so sounds a little more enthusiastic, whereas 'could' can sound slightly more hesitant.  However, these are very minor differences, and often the way that you say it (the pronunciation) is more important than the choice of 'can' or 'could'.

I hope that clarifies it for you.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by vikramkbc on Sat, 21/09/2013 - 18:42

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What form of the verb are used with 'can be'? Can we use 1st form of verb with can be?

Hi vikramkbc,

Modal verbs like can are followed by the first form of the verb when speaking about the present.

When you ask about can be, be is the first form of the verb, but you could put the first form of any verb after can, e.g. can speak, can write, etc.

Is this what you were asking about?

Best wishes,

Kirk

The LearnEnglish Team

Submitted by Monty Stevens on Sat, 21/09/2013 - 06:34

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Hi sir could you please help with this sentence?I'd be really grateful i mean i just don't know if it's referring to the past or future. The sentence is, we could be doing a lot worse,

Hi Monty,

In this sentence, could be doing is referring to the present, specifically to the idea that it's possible for the present situation to be different now, depending on how things went in the past (see the last explanation under Possibility above).

Best wishes,

Kirk

The LearnEnglish Team

Submitted by Monty Stevens on Tue, 03/09/2013 - 05:13

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Hi sir can you help me with this sentence? You couldn't possibly love me as much i do

Hi Monty Stevens,

I'll be happy to help you, but I'm not sure what the problem is!  The sentence is correct, but has a rather odd meaning - it sounds like the speaker is saying that they love themselves more than the other person could, which is rather egotistical to say the least!

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by monnzz on Tue, 30/07/2013 - 13:09

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Hallo, Peter, thanks for having patience with me and answering my questions:)

what about this example:

here is some background: "Me and some friends went camping and the next morning we discovered that one of our friends missing, so

Our friend could lose his way in the dark.

Our friend could have lost his way in the dark.

 

Honestly, Im not sure this example is what we need in this particular topic, because i believe i need to use "could have lost" here, because of that is one of explanations why our friend lost his way. (perhaps, he didn't like camping and went home not notifying us)

So is it possible to remake this situation somehow so we could use "could lose" instead? 

 

P.S. So we can use "would" to show typical behaviour such as, for example:

I would usually go for a walk in the evening.

(But could i just say: I usually go for a walk in the evening?) Does it mean the same? 

 

Hello monnzz,

In your first example I think 'could have' is necessary.  If we weren't talking about a specific situation but rather indulging in general hypothetical speculation about the possibility of getting lost then 'could' would be possible.

In the example you give 'would' describes a past habit, similar to 'used to', rather than a present habit.  The use of 'would' in my sentence is quite a tricky one, and it usually appears when we contrast characteristic behaviour or choices of different people.  For example:

People in my country like to go for a walk in the morning.

Oh, really?  In my country people would usually go for walks in the evening.

As I said, this use usually carries a meaning of 'would choose/like/prefer/opt for'.

Best wishes,

 

Peter

The LearnEnglish Team

Submitted by monnzz on Thu, 18/07/2013 - 09:01

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Hallo, your lesson is very helpful, but there is still one unclear situation for me:)

Could you explain to me what the difference is between "could" and "could have" when we want to express possibility in the past?

for example:

I don't know that could have been John. 

I don't know that could be John. 

In both cases i imply, that I'm not sure if it was John.

So which one is right and why?:)

Any help would be much appreciated, thanks in advance:)