'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

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can and could: other uses 2

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Soumis par LitteBlueGreat le mer 24/11/2021 - 01:33

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Morning sir

I have a question on difference between "Must have" and "Could have"

Could the both be used when we want to guess or predict and are just different in level of certainty in which "must have" is strongest?

Thank you

Hello LittleBlueGreat,

We use both 'must have' and 'could have' when we don't have direct knowledge of something.

As you say, 'must have' shows we are more certain; often, it means we are quite certain because nothing else makes any sense or because our idea seems very likely. For example, if I go into my kitchen and see a broken window and a stone on the floor, I might say 'Someone must have thrown a stone at the window'. I did not witness this, but I can infer that this is what happened. Unless there's some recording of this from a security camera or unless someone witnessed it, I can't really know completely for sure, but it seems pretty likely.

'could have' shows that we are not certain; perhaps we are making a guess, or perhaps we are stating a possibility someone else hasn't thought of -- it really depends on the context. Returning to the example of the broken window in the kitchen, imagine that there is no stone on the floor, nor any other indication of what happened, but the window is right next to a construction site. Here I might say 'A worker could have broken the window by accident'. Like before, I don't know, but because there is no sign of what happened, I'm clearly making a guess. I could also say 'A worker must have broken the window' if I feel more certain about that. It really depends on my point of view.

Hope that helps.

All the best,
Kirk
The LearnEnglish Team

I got it Sir

An another question for explanation, If the case is replaced with "Can" and "Must" Could the same rule be applied again where "must" is more certain?

Thanks again

Hello LitteBlueGreat,

'must' expresses the same idea as 'must have', but I'm afraid it's more complicated with 'can'.

As is explained in the 'Possibility and impossibility' section above, 'could' can be used to talk about the probability or possibility of something happening.

But 'can' isn't used in this way. When the explanation says 'We use "can" to make general statements about what is possible', it means that we can use 'can' to talk about what is common (e.g. 'It can be very cold here in winter') or what is possible because a specific situation makes us able to do something (e.g. 'I can stay home today because it is a holiday'). In this last example sentence, the fact that today is a holiday makes me able to stay home -- it's not talking about possibility so much as ability.

I hope this helps.

All the best,
Kirk
The LearnEnglish Team

Soumis par Plokonyo le jeu 18/11/2021 - 05:24

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Why do we use "could" in this sentence? What if I replace it with "can"? Is there any difference?

We often use 'would' to describe different options to choose from. You could use the present simple here as well.

Hello Plokonyo,

Both 'can' and 'could' are possible. 'Can' suggests a real situation (you are really going to say this) while 'could' suggests we are discussing the issue hypothetically (one day you might need this).

Peter
The LearnEnglish Team

Soumis par Crokong le ven 24/09/2021 - 04:10

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My English grammar says that "could" a less difinite form of can. What is meant by "less definite" form? Does "could" mean "not definite"? Could is not only past: we also use it as a 'softer’, less definite form of can. 'What shall we do tomorrow?’ ‘Well, we could go fishing.' When you're in Spain, you could go and see Alex.

Hello Crokong,

As you know, most modal verbs have a number of different uses and can and could are no exceptions. Both can be used to make suggestions:

What shall we do tonight?

We can watch a film if you like, or just go for a drink.

We could watch a film if you like, or just go for a drink.

Could is a little more tentative in these kinds of sentences, I would say, which is probably what your grammar book had in mind.

 

Peter

The LearnEnglish Team

Thanks, Peter. What is meant by "tentative" is to make the speaker sound less dogmatic or open for other opinion. What do you think?

Hello Crokong,

Yes, that's right. The speaker is a little less certain of his or her choice, claim, suggestion or opinion.

 

Peter

The LearnEnglish Team

Soumis par amit_ck le mar 14/09/2021 - 07:34

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It is not money that can solve children's problems, but love and good teaching. Is this sentence okay? If it is, then why they didn’t use CAN at the end of the sentence? Like; but love and good teaching can. Could you please explain it and also give me some examples of this kind of sentence?

Hi amit_ck,

Yes, the sentence is correct! Here is the basic structure, with some examples. 

  • It is not A but B.
  • It's not Jim who I need to see, but Tony.
  • It's not red apples but green apples that she likes.
  • It's not the things I know but the things I don't know that I worry about.
  • It's not money that can solve children's problems, but love and teaching.

A and B are noun phrases (underlined). Can is part of an added clause, not part of the A noun phrase. That's why it's not added to B at the end of the sentence.

You could add 'can' at the end for extra emphasis. In this case, I'd probably say it like this, to separate the two clauses:

  • It's not money that can solve children's problems. Love and teaching can.

I hope that helps :)

Jonathan

The LearnEnglish Team

Soumis par DaniWeebKage le ven 11/06/2021 - 11:26

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Dear Team, I have some confusion about the possibility of can and could. It says 'can' is used with general statements while 'could' is used when it is possible but not certain. Then, 1) You can be lost in town. 2) You could be lost in town. 1.What is the difference between these two sentences. And my teacher once said 'can' is used with strong possibility while 'could' is with less one. 2.Is that correct? From my point of view, it all depends on the speaker's view which he considers one as a certain thing, he might use ' can ' and one as not a certain thing , he might use ' could '. 3.Is mine correct?

Soumis par Peter M. le sam 12/06/2021 - 07:03

En réponse à par DaniWeebKage

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Hello DaniWeebKage,

Your first sentence is not correct as it appears to describe a current situation (being lost); this would mean that you are speculating rather than describing what is generally possible. Note that in the example on the page the verb is 'get lost', which does not describe a current state. Your second sentence is fine. It expresses speculation about the present and has a similar meaning to 'maybe' or 'perhaps'.

 

You can get lost easily in this town. [a general statement about the town: it is possible because the town's layout is confusing]

You could get lost easily in this town. [a specific statement about your trip: there is a chance of this happening]

 

Peter

The LearnEnglish Team

Thanks a lot, Sir Peter, 1)In which situation should be use 'You can be lost in this town" ? 2) Does 'Can' mean more possibility to happen than 'could'? All the best.

Hello again DaniWeebKage,

We wouldn't use this formulation. To speculate about what may or may not be true at the moment we use could (You could be lost).

Can describes something which is not impossible. Of course a person can be lost, but it is a banal statement without any real meaning.

 

Think about it this way: when we are talking about how a person feels we say 'He could be angry', meaning 'there is a chance he is angry'. We don't say 'He can be angry' because it is obvious: anyone can be angry at any time.

 

Peter

The LearnEnglish Team

Soumis par nsnaveensorout le mar 16/03/2021 - 05:15

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Can we say "Could" is used for Future possibility ?

Hello nsnaveensorout,

Yes, that's one use of 'could'. It can describe present or future possibility, as the first two examples on the page show:

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

They could come by car. (= Maybe they will come by car.) - future possibility

They could be at home. (= Maybe they are at home.) - present possibility

 

Peter

The LearnEnglish Team

Soumis par Dwishiren le mar 23/02/2021 - 14:14

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Sir sometimes I see you said 'you could use', what is the difference between you can use and you could use? You can use 'but' to join these as one sentence. You could use 'but' to join these as one sentence

Hello Dwishiren,

When we make suggestions both are often possible and have verb similar meanings. We can use can with a general (this is possible) or specific meaning, while could tends to be specific to a situation (in this situation it is possible).

 

Peter

The LearnEnglish Team

Soumis par Crokong le lun 22/02/2021 - 03:29

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Hi sir.I wondering what 'could' means in the following sentences? Drive carefully or you could have an accident. David is coming to visiting. He could stay with us.

Hi Crokong,

You have two different uses here.

In the first example, could expresses possibility and has a similar meaning to might: this is something that has a chance of happening.

In the second example the meaning is also about possibility but in the sense of making an offer or a proposal. Here, it has a similar meaning to able to: we are able to give him a place to stay.

 

Peter

The LearnEnglish Team

Soumis par mary_1565 le jeu 18/02/2021 - 11:09

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the sentence: If Jones was at work until six, he couldn't have done the murder. is right according the conditionals rules?

Soumis par BobMux le mar 26/01/2021 - 13:11

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Hello The LearnEnglish Team, I would appreciate it if could help me understand why "CAN" is used in these context below, i mean, what "CAN" means here e.g. possibility, permession.... We help you progress quickly because of the intensity of the training. You CAN expect to be taught in a safe invironment, with the minimum of risk.
Thanks a lot Kirk, I wish you and The LearnEnglish Team all the best! You really are helping me!

Soumis par Rsb le lun 11/01/2021 - 06:39

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Sir, I saw an advertisement on the television to save the child. The last line of advertisement was that: You could help save the child. What 'could' shows here a request?

Hi Rsb,

Yes, I think it's a suggestion too! It could be a request if it was in the question form: Could you help?

Best wishes,

Jonathan

The LearnEnglish Team

Soumis par Gloria Pérez le jeu 07/01/2021 - 17:01

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Hello Kirk, I have a doubt about the different verb patterns used for the verbs "to recommend", "to suggest" and "to advise" as, depending on the source consulted, some patterns are accepted and some are not. I will list down only those patterns on which different book texts don't agree (so I am not sure whether they are right or not): RECOMMEND / SUGGEST: 1/ Subject + verb + someone-object + to infinitive Is this structure RIGHT or should a passive be used instead? Some books say it is not! Ex: The doctor recommended/suggested him to do exercise (right or "He was recommended/suggested by the doctor to do exercise" must be used instead??) Or CAN this pattern be used for "to recommend" but not for "to suggest"?? 2/ Subject + verb + (someone or to someone)? + that + .... Ex: The doctor recommended/suggested (me/to me) that he should do exercise RECOMMEND / SUGGEST / ADVICE: 3/ Subject + verb + that + someone-subject + BASE VERB Ex: The doctor recommended/suggested/advised that he DO exercise (whether it's present -regulary) or past (those months)) or should it be: - the doctor recommended/suggested/advised that he does exercise (regularly) - if it's present ("haga") - the doctor recommended/suggested/advised that he did exercise (those months) - if it's past ("hiciera/hiciese") Thanks for helping me to clarify this. Gloria. PS. And happy new year ;-)!

Hello Gloria,

I'm not in a position to say that other text books are wrong, but I can tell you what I understand to be correct.

I would not use pattern 1 with 'recommend', but in at least one of my reference books, it is listed as correct, so I would go with that. Neither I nor my reference book consider pattern 1 correct with 'suggest'. In general, I would avoid the passive here, even though it might be grammatically correct in some cases.

I'm not sure if pattern 2 is incorrect or not, but I'd recommend avoiding it. If it's really necessary to specify that the advice for another person was given to a different person, I'd use a couple of sentences to explain that.

As for pattern 3, as far as I understand it, only 'do' is really correct here. This is an example of the subjunctive, which is far less developed in English than in Spanish; in this case, 'do' is a translation of both 'haga' and 'hiciera/hiciese' and so you'd need some other phrase (or the context) to make it clear if the recommendation is speaking about the present/future or the past.

I should mention that most native speakers of English don't know what the subjunctive is, and so you might find them using 'does' or 'did' where I've said you should use 'do'. I believe most editors, though, would recommend 'do' here.

Hope that helps. Happy New Year to you too!

All the best,

Kirk

The LearnEnglish Team

Soumis par Stellaaa le mar 29/12/2020 - 11:24

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I'm still confused about general & specific ability

Hi Stellaaa,

You can use 'can' to speak about someone's ability to do something in general ('She can swim'), and you can also use it to speak about how they manage to do something in a specific situation ('I can help you now').

You can use 'could' to speak about someone's ability in the past ('My grandmother could speak Swedish') but not to speak about how they managed to do something in a specific situation (not 'The fire brigade could rescue the child', instead: 'The fire brigade was able to rescue the child').

All the best,

Kirk

The LearnEnglish Team

Soumis par Yigido le ven 25/12/2020 - 14:11

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Hi team, "He couldn't be a basketball player.He isn't tall enough.''Teacher in this sentence I think - could- use for probability because" He isn't tall enough."Present simple.But In my book says - could- use for ability. Which one is right?I think mine.

Hello Yigido,

All of the modal verbs have several different meanings and uses. In this case, it sounds to me as if 'couldn't' is speaking about a hypothetical situation: if he wanted to be a basketball player, he could not be one because he isn't tall enough.

Does that make sense?

All the best,

Kirk

The LearnEnglish Team

Actually teacher sentences are ''He__be a basketball player. He isn't tall enough.''Answer key says couldn't. I mean it does not say about which meaning.I am still confused If ıt was hypothetical situation,why wouldn't sentences like that?

Hello Yigido,

I think I'd recommend you ask your teacher about this one, as he or she will know what exactly the mean to say. In general, though, 'could' refers to ability in the past, or, as I mentioned, it can refer to a hypothetical situation (with the meaning of 'would be able to').

Hope this helps.

All the best,

Kirk

The LearnEnglish Team

Actually, I don't have real teacher. I say "teacher"to people who are explain grammar rules in YouTube.

Soumis par Salum Hilali le mar 08/12/2020 - 09:11

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I could have learned a lot,but i did not know about this site before.

Soumis par Mison le lun 30/11/2020 - 02:31

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Suppose that, our team want to take a chellenge and we are making suggestion and we says "we could do it".does this sentence sounds right

Soumis par aliakar86 le lun 14/09/2020 - 13:35

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Hi I want to ask about usage of '' Must not'' negative form of Must in past Can I use ''Mustn't have v3'' in Past strong advice and past prohibited.For exapmle can I say ''Last night you was sic.You must not have gone to outside'' (Strong advice) and talk about past prohibited can I say ''You mustn't have sold cigarette under 18 20 years ago'' ? İt may be still forbidden or not now.But that time it was forbidden.Last question Can I use ''must have '' past advice like ''should have'' for example can I say ''you failed exam you must have studied hard'' otherwise can I use ''mustn't have done'' only past strong deduction ? For Exapmle: I saw my friend's car in front of his home and I can say 'He mustn't gone work by his car''

Hello aliakar86,

I'm afraid that it's not correct to use 'mustn't have' in the ways you ask about because in English you can't prohibit something that already happened. For example, it's not correct to say to your friend 'You must not have gone outside' -- instead, you should say 'You shouldn't have gone outside'.

Similarly, to your friend who got poor exam results, you should say 'You should have studied more' instead of 'You must have studied more'.

It is correct to use 'must have' for deductions. You can see more about this on our Modals – deductions about the past page. I think that should be quite clear, but if you have any more questions, please let us know.

All the best,

Kirk

The LearnEnglish Team

Soumis par IsabelTim_123 le ven 11/09/2020 - 12:37

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These animals can be dangerous. - Is it the same as These animals may be dangerous? Many thanks.

Hello IsabelTim_123,

'may be', 'might be' and 'could be' would all mean the same thing in this sentence: these animals are possibly dangerous, but I'm not sure. You might say this, for example, when you see some animals you're unfamiliar with (e.g. wild pigs) and you really don't know anything about them. But since they are wild animals, there is the possibility that they are dangerous.

'can be' is used to speak more about a possibility we are familiar with -- it suggests that you know something about the animals. If, for example, you see those wild pigs and know for a fact that in some situations they are dangerous --perhaps your grandfather told you this -- and using 'can' would express this idea. Perhaps they won't be dangerous in this situation, but you know that in some cases they are.

Hope this helps you make sense of it.

All the best,

Kirk

The LearnEnglish Team

Soumis par smit le jeu 10/09/2020 - 08:22

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Could is use for past ability and for possibility, how we can know in what meaning could is used for in sentence

Hi smit,

Yes, that's right! To work out which meaning is intended by a speaker or writer, we need to consider the context. That includes other things the speaker or writer says, and details about the situation (e.g. the place, the time, the relationship between the speakers, other topics in the conversation).

 

The examples above are isolated sentences, so they don't have much contextual information. For example, one sentence above is:

  • She could speak several languages.

But, in real speaking or writing, it would have more context, for example:

  • Sara's so good with languages. Even when she was little, she could speak several languages.

The context gives us clues (e.g. when she was little) to show that could means 'past ability' here, and not 'possibility'. 

Does that make sense?

Best wishes,

Jonathan

The LearnEnglish Team

Soumis par smit le jeu 10/09/2020 - 19:46

En réponse à par Jonathan R

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Yes, but what about below example You :- Sarah can speak English? Me :- she Could (as I'm not 100% sure about answer)