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
- can and could: possibility 2
- can and could: other uses 1
- can and could: other uses 2
Hello, l have a question.
Amy to Jack- you are spying on me.
How could you do that to me?
In the above sentence could refers to past or present. Does this sentence mean How were you able to do that to me? Or How can you do that to me?
Hello jitu_jaga,
Modals have multiple uses. Sometimes 'could' describes past ability:
In this case you can replace 'could' with 'was able to':
However, sometimes 'could' describes possibility, and then 'was able to' is not an alternative: The speaker in your example is asking 'How is it possible that you did this?' with the sense of 'I did not believed you were the kind of person who would do this'.
Looking at possible responses may help to clarify:
Peter
The LearnEnglish Team
Please i need a little bit education on this. Why is it that you could say "I haven't bought a car'' but you can't say" I couldn't bought a car?
Hi lordstone,
It's because the auxiliary verb "have" should be followed by the past participle form of the verb (e.g. buy --> bought).
"Could" should be followed by the base form of the verb ("buy"), not the past participle.
I hope that helps.
Jonathan
LearnEnglish team
Hello, l have a question.
Amy to Jack- you are spying on me.
How could you do that to me?
In the above sentence could refers to past or present. Does this sentence mean How were you able to do that to me? Or How can you do that to me?
Hello jitu_jaga,
It's more of a hypothetical meaning -- it's as if she were saying 'How could you do that to me if you respected me?'.
All the best,
Kirk
LearnEnglish team
I have a question. I know that we can use 'can' to talk about permission in the present like 'I can wear jeans to go to school' meaning I'm allowed to wear jeans to go to school. My question is: is it possible to use could in the negative form, couldn't, to talk about permission in the past like 'when I was a teenager I couldn't wear jeans to go to school' meaning I wasn't allowed to wear jeans to go to school. To me if I use couldn't it gives the idea of hability and not permission. It sounds more natural to use 'be allowed to' in this context. Please correct me if I'm wrong. Thank you.
Hello Rejane,
All modal verbs, including 'can' and 'could', have several meanings and uses. The sentence you ask about could mean you weren't allowed to wear jeans, or it could mean that you were not able to wear jeans (for example, if you didn't have any), or it could probably mean other things. The context would normally make the precise meaning clear or the sentence might just be ambiguous.
By the way, please only post your questions once. As you'll have seen, it takes a little time for your comments to be published and publicly visible, but we will publish them as we can.
All the best,
Kirk
The LearnEnglish Team
Thank you for your answer. As I understand, both, could and couldn't can be used in the past form to mean permission or hability, it will depend on the context. Thank you
They could/may/might lose the match.
How can we say this in past tense?
We thought they could/may/might have lost the match, but at the end they won.Is it correct ?
Hello Faii,
It's really a perfect form rather than past tense, but your example is fine. If we say 'could have lost' then without any other information we don't know if the match was in fact lost or not. If you add a second clause like the one you have (but...) then it becomes clear what the final result was.
Peter
The LearnEnglish Team
Is it correct to say "He can get here at any time " if we want to mean that there is a strong possibility?
Hi Faii,
If you are talking about one particular occasion (e.g. the person is coming here right now), then I would prefer to use "could" in this sentence for that meaning.
"Can" for possibility is a more general statement. For example, perhaps you are talking about this person's arrival time not on one particular occasion (e.g. today), but as a more general and repeated action (e.g. the time he comes here every day, not just today). So, yes, you can use "can" for that meaning but it gives the idea of a more general action.
I hope that helps.
Jonathan
The LearnEnglish Team
Thanks for your explanation. I got it.
I have another question.Can we use "can" to make a suggestion?If yes,then what's the difference?
Hi Faii,
Yes, we can use "can" to make suggestions, although "could" is more typically used. As for the difference, "could" is less direct and may be considered more polite.
Jonathan
The LearnEnglish Team
What is the difference in the following sentences:
You can't have seen him, he is on holiday
You couldn't have seen him, he is on holiday
Thanks for any help.
Hi MarCap,
They mean the same thing - this past event (seeing him) was impossible!
Jonathan
The LearnEnglish Team
I could read that book in two hours yesterday . Please explain Why this sentence is wrong ?
Hello salimm,
You can use 'could' to talk about ability to do things in general in the past. For example, if you lived next to the sea when you were young, you could say something like 'I could go fishing every day' to mean that it was possible for you to do that since you were so close to the sea.
But when we're speaking about what we did or accomplished in a specific situation in the past, we can't use 'could' to speak about what it was possible to do or what we did at that time. For example, it would not be correct to say *'On my 12th birthday, I could catch a huge fish'. Instead, we use 'managed to' or 'was/were able to' or just the past simple: 'On my 12th birthday, I managed to catch/I was able to catch/I caught a huge fish'.
The sentence you ask about speaks about something you did yesterday, so 'could' doesn't work for the same reasons. Instead, you should say 'was able to read', 'managed to read' or 'read'.
You might find it useful to read a little more about this and do a couple of practice exercises on our Past ability page.
All the best,
Kirk
The LearnEnglish Team
Hi
What is the time of the following sentence (with no other word showing the time):
"She could speak English."
Two potential meaning may arise:
It refers to the past that means she could speak English in the past.
It refers to a possibility in the present time that means she may speak English now.
Please clarify.
Regrads,
Hamid
Hi Hamid,
Your interpretation is correct. In fact, 'could' here has three possible meanings:
These are possible meanings; without any context we can't say which is the actual intended meaning.
Peter
The LearnEnglish Team
Howdy teachers.First of all thank you all for providing precious knowledge for us. What is the difference between " How couldn't you know?" and " How could you not know?"
Hello Sa9014211121,
The first sounds very strange to me; I can't think of a situation when I'd say that, though this may say more about my lack of imagination than the grammar! If you've seen this in writing somewhere, please give us the context.
The second one expresses incredulity at the idea that the other person doesn't know whatever is being referred to. If you said this to me, it would mean that you think it's impossible that I didn't know something.
Hope this helps.
All the best,
Kirk
The LearnEnglish Team
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
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
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:
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
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
Hi amit_ck,
Yes, the sentence is correct! Here is the basic structure, with some examples.
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:
I hope that helps :)
Jonathan
The LearnEnglish Team
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
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
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:
Peter
The LearnEnglish Team
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
Hello sir,
I still have a doubt about the difference between the followings
You might use 'can' to make requests in a friendly way.
You could use 'can' to make requests in a friendly way.
Both could and might are used to make suggestions. So, pls tell me the subtle difference between them so that i will be able to satisfy my students with that subtle distinction.
Thank u, sir.
Hello Kumaraswamy,
You're right that any distinction here is very subtle and would likely be overwhelmed by aspects such as tone and expression. That said, to my ear could sounds more neutral ("here is a possibility") while might implies more of a personal opinion ("I think this is the best choice").
You can read a discussion on the topic here:
https://ell.stackexchange.com/questions/20003/might-and-could-used-for-making-suggestions
Peter
The LearnEnglis
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
Hi mary_1565,
Yes, it's grammatically correct :)
Jonathan
The LearnEnglish Team