'can' and 'could'

Learn about the modal verbs can and could and do the exercises to practise using them.

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: Matching_MTYzNjc=
can and could: possibility 2: GapFillTyping_MTYzNjg=
can and could: other uses 1: Matching_MTYzNjk=
can and could: other uses 2: GapFillTyping_MTYzNzA=

Do you need to improve your English grammar?

Join thousands of learners from around the world who are improving their English grammar with our online courses.

Find out more

Thanks for your detailed reply! But am I correct to say that those two sentences refer to express future possibility and future ability respectively? If that is the case, I am confused about why "can" is used because I have the belief that "can" should not be used to talk about future possibility (expressed by could, may, might) or future ability (expressed by will be able to).

Hello again AsahiYo20,

The first sentence does not express future possibility but rather describes the present situation. It could be an answer to a question such as 'Why isn't the restoration work being done?', for example.

The second sentence is also not about the future. It describes a person's job in general terms, not a particular future event. It would be an answer to a question such as 'What does your job entail?' and not 'What are you doing next week?'

Peter

The LearnEnglish Team

Hi teachers, 1. Her colleagues could not fault her dedication to the job. --> Assuming that this sentence is not talking about the past, could I change "could not fault" to "cannot fault"? 2. The doctor examined her carefully but could find nothing wrong. --> could I delete "could" in this sentence? (i.e. ...but found nothing wrong.) Thank you.

Hi patph0510, 1. 'Could' is referring to the past in this sentence. To say something is impossible in the present, we use 'can't' – but not 'couldn't' (see the first section above for some examples). So, your sentence with 'cannot fault' is the correct one for the present meaning. 2. Yes, you could. The meaning would be very similar, but with one difference: the version with 'could' includes the meaning of the doctor attempting or making effort to find the problem. The version without 'could' doesn't include that, and is focused on the end result (finding nothing wrong). Best wishes, Jonathan The LearnEnglish Team

Hi teacher, Thank you for your reply. As you said, and also according to a number of grammar books I have read, to say something is impossible in the present, we use 'can't'. But I sometimes see sentences using 'could (in a negative context)/could not' that seem to suggest impossibility in the present. Could you explain why 'could' is used in the following sentence? "Nobody could take serious issue with his endorsement of the principle that police officers must be deterred from breaking the very laws they are empowered and entrusted to uphold"

Hi brian1010,

I can't be absolutely sure without knowing the full context of the sentence. But I think it's fine to use Nobody could ... to mean impossibility in the present because it uses could – not couldn't. If we make a version of the sentence using couldn't:

People couldn't take serious issue with ...

It isn't equivalent in meaning. It would be understood as referring to a past ability, not a present possibility. As you've seen above, could and couldn't have nuances in their meanings and aren't exact opposites, so could with a negative subject (e.g. Nobody could) isn't the same meaning as couldn't (for the meaning of possibility, at least).

For other meanings, could and couldn't may be more direct opposites. The sentences below about ability do have the same meaning.

Yesterday, nobody could answer the question.
Yesterday, people couldn't answer the question.

Does that make sense?

Best wishes,

Jonathan
The LearnEnglish Team

Hi teacher, Are you referring to this section above: "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.)" Does that mean we cannot use "could not" to convey a negative meaning in the sentences above because only "could", not "could not", can indicate a present possibility? Should we use "may not" instead if we want to convey a negative meaning? Thank you.

Hi brian1010,

Yes, that's right. To say that those things are impossible for them to do, we can use can't or cannot, but not could not.

They can't come by car.
They can't be at home.

Using may not is possible, but the meaning is a bit different. May often indicates permission, so if we say They may not come by car, it means 'they cannot come by car because they don't have permission'. This usage of may not is also quite formal and emphatic.

Also, it might be confused with the 'not sure' meaning of may. They may not come by car (if there's no other context) would probably be understood as meaning 'I'm not sure whether they'll come by car or not', which is different from They can't come by car. So, I wouldn't recommend using may not for this meaning.

See this page for more explanation and examples about may: https://learnenglish.britishcouncil.org/english-grammar-reference/may-and-might

Best wishes,

Jonathan

The LearnEnglish Team

Thank you for your detailed reply. I would like to ask one more question as I just came across a sentence, which reads: "No one can say what might not happen if there were another earthquake." I notice that the writer uses "can" rather than "could". Does that mean in the sentence I referred to earlier ("Nobody could take serious issue with his endorsement of the principle..."), "can" is also an acceptable alternative?

Hello brian1010,

Yes, you could use can in your sentence. Could has a distancing effect, making the sentence more hypothetical; can makes the sentence more immediate, as if describing a real situation. The difference is really only one of nuance, however.

I think your sentence about the earthquake may have an error. The phrase '...what might not happen...' seems odd; '...what might happen...' is more likely, I think.

Peter

The LearnEnglish Team

Hi teacher, In the following two sentences, could I use "could" instead of "would"? Would there be any difference in meaning? 1. Would you lend me the car tomorrow night, Dad? 2. Would you fill in this form, please, sir? Thanks.

Hi teachers, Not sure if you have missed my question. I would appreciate it if you could give me a reply. Thanks!

Hello brian1010,

Yes, somehow we missed your question -- sorry about that!

In both sentences, some might argue that 'would' speaks more of willingness and 'could' speaks more of ability, but in most cases, both forms would be correct and mean the same thing.

All the best

Kirk

The LearnEnglish Team

Could you please tell me the difference between : I might be able to come today vs I might come today

Hello Ballou1982

The first one implies that the main thing is whether you can or cannot come today. You don't know yet if something might stop you from coming. For example, if your friend has invited you to visit him, but you think you will have to work, you could say this because if you have to work, you can't visit your friend.

The second one is less specific. It just says that perhaps you will come or perhaps you will not. It could be due to work, it could be because you don't want to, it could be anything, really, that prevents you from coming.

Hope this helps.

All the best

Kirk

The LearnEnglish Team

Hello teachers, I am back with a question. It is about "Later" and "Later on". The difference, though being distinct to me, can sometimes get me. I am sure u can help me with its distinction precisely. Could you tell me when to use " later" and "later on"?

Hello GIRIKUMAR,

As far as I am aware, there is no difference in meaning. Later on is a little more informal.

Later is often used as an informal way of saying goodbye, with the same meaning as See you later.

Peter

The LearnEnglish Team

Hello teachers, hope you are all doing great. In the Oxford dictionary, the meaning of the phrasal verb "mess up" has the verb 'fail' not with the preposition 'in' but 'at' when it's supposed 'in' as regards one of the examples below the first meaning concerned with the verb 'fail' in the same dictionary. The sentence goes thus, Mess up: to fail at something or do it badly. My question is, What's the difference between "fail in" and "fail at"? When should we you 'at' and 'in' with the verb 'fail'? Thank you, teachers.

Hello GIRIKUMAR,

I don't think there is a difference in meaning. Rather, there are certain typical patterns of use.

We tend to use fail in with words related to trying something: fail in your attempt, fail in your plan.

We tend to use fail at with activities: fail at the task, fail at the final test

I think fail on its own, or fail to [verb] are much more common forms, however.

Peter

The LearnEnglish Team

I m sorry to post this question despite being irrelevant here. I request that you answer it just like you do regularly in order not to fail us, teachers. That's the only reason why I come over here hopefully. In return, all I can do is express my gratitude in mere words like "Thank you so much". Could you tell me the differences between, " yourself, to yourself, and for yourself", teachers? I saw a phrase on YouTube that goes like, "understanding your values to yourself". Can we say it without " to". I did it myself. I did it to myself. I did it for myself. What do they mean despite looking like they mean the same? Thank you, teachers.

Hello GIRIKUMAR,

Myself can be used in several ways, as you show.

I did it myself (nobody else helped me) - this means that I did the task and nobody helped me; I did it alone.

I did it to myself (and nobody else was to blame) - this is generally used to describe unfortunate situations and it means that the speaker blames him- or herself; nobody else is responsible.

I did it for myself (not for you) - this is generally used to describe positive situations and it means that the speaker's motivation was their own benefit rather than the need or wish of someone else.

Peter

The LearnEnglish Team

Hello teachers, Hope you are doing well and you should be doing well or we would not be able to get our doubts clarified. We are very grateful to you indeed. Could you tell me which one of the following sentences is correct and why? Last night I went to a function. Last night I went for a function. Regards.

Hello Girikumar

The first one is correct because we use 'to' to speak about a destination. I'm assuming that 'function' here means 'a social event', as otherwise I wouldn't really understand what these sentences mean.

Thanks! Hope you also are doing well.

All the best

Kirk

The LearnEnglish Team

I am in the meeting now. I am at the meeting now. What do the two sentences actually mean? Which one of them should we use when talking about the fact that we are involved in it?

Hello Girikumar

I'd probably say 'in' here, but I think both 'in' and 'at' are fine. As far as I know, there's no difference in meaning between them.

There's a good explanation of the differences in use between the most commonly used prepositions of place on this page if you're interested.

All the best

Kirk

The LearnEnglish Team

Sir, Could you tell me the difference between, "When would you come tomorrow?" and "When will you come tomorrow?" Thank you.

Hello Girikumar

Could you please search our site for an appropriate page to ask your questions? For example, in this same Verbs section, there is a page called 'will' and 'would'. I expect the explanation there will answer question, but if not, please feel free to ask us. We just ask that you try to ask your question on a relevant page.

All the best

Kirk

The LearnEnglish Team

Hello Sir, As usual I am in need of your help to understand the subtle differences between "sure of" and "sure about", "confident of" and "confident about". Despite the fact that I use them correctly, I tend to confuse them with the other ones at times. Thank you, sir.

Hello GIRIKUMAR,

As far as I am aware there is no difference in meaning between sure of and sure about. I don't know of any context where only one would be correct, though there are certain phrases where one is preferred, such as when using a reflexive pronoun (sure of yourself rather than about).

Peter

The LearnEnglish Team

Hello Sir, 1) kill him before he can kill you. 2) kill him before he kills you. Is there any difference between these two sentences. If yes then what meaning two sentences convey. Thank you.

Hello Abhinav,

In most contexts, the sentences can be used interchangeably.

Can carries the meaning of 'has the ability to', so you could imagine a situation in which you want to stop a person getting the ability to kill. For example, you might want to act so that someone is prevented from getting hold of a weapon which would make it possible for him to kill you.

Peter

The LearnEnglish Team

I can't find the function related to these uses of CAN: You can leave your hat on that chair He won't love you as much as I can I think he's angry with you but you can call him to check it out.

Hello Dayan

In the first sentence, 'can' seems to be used to give permission to someone. The second sentence seems a little odd to me (I think I'd say 'do' instead of 'can'), but I suppose it's describing an ability. In the third sentence, I'd say it's speaking about possibility.

Hope that helps!

All the best

Kirk

The LearnEnglish Team

Dear Sir, I have just registered at LearnEnglish. I am so happy that I can get my doubts clarified by the full-fledged teachers who are so responsive to whoever is in need of clear and precise answer to their questions concerned with grammar. You in fact make boring and confusing grammar interesting and easy to learn. My question is, You have said that 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. In the first sentence above, it's understandable that "can't have" is used as the verb in its preceding sentence is in the present. So is in the case of the second sentence. What if we used "can't have" when we talk about a past action. For instance, I heard someone knock on the door.It can't have been our neighbour. Thank you.

Hello GIRIKUMAR,

While could can function as the past form of can when describing ability (I can swim vs I could swim), here you are using them for (im)possibility. In this use, they are interchangeable in many contexts. However, can't have is generally used for more recent contexts and couldn't have for ones further back in time.

You can read more about this in the discussion on this page:

https://english.stackexchange.com/questions/141589/cant-have-been-vs-couldnt-have-been

Peter

The LearnEnglish Team

I don't think I will be wanting for any better explanation than that of yours. Thank u so much, sir.

Dear Sir, Kindly tell me the exact meaning of the following sentence. I personally feel that it has two meanings 1) Anyway he came here yesterday. 2) He had the possibility to come here yesterday, but he didn't come. I would like to know whether my understanding is correct. Kindly advise me on this. 1) He could come here yesterday. Thank you.

Hello Aniyanmon,

The sentence does not look correct to me. You could say either of these:

He could have come here yesterday. [it was possible but he did not come]

He was able to come here yesterday. [it was possible and it is not clear if he came or not]

He could come here yesterday is incorrect because it implies some kind of time travel: a present or future possibility (He could come here) with a past event (yesterday).

Peter

The LearnEnglish Team

Thanks a lot sir.

Hi all, I have a question. Is it possible to use "could not be able to" in any context? Thanks in advance.

Hello japezuela,

I think would not be able to... is far more likely in any context I can think of. Did you have a particular context in mind?

Peter

The LearnEnglish Team

Hi Peter, Thanks for answering. I was thinking of, for example, in a situation in which it was too difficult for me, or out of the question, to be able to. Could I say, ' I could not be able to play a piano' referring to a past situation meaning " it was too hard for me playing the piano because I didn't have the necessary skills for doing so? Thanks in advance.

Hi japazuela,

In that situation we would use either 'able to' or 'could', but not both together:

I could not play the piano.

I was not able to play the piano.

The only time we might use 'could' and 'able to' together is when we are using 'could' to talk about possibility rather than ability. In other words, 'could not be able to' might mean 'it is possible that [he/she] would not be able to...'

However, it is hard to think of a situation where we would use such a form, and I think other less ambiguous forms would be preferred in any case, such as 'could be unable to', 'might not be able to' or 'might lose the ability to'.

Peter

The LearnEnglish Team

Need your help in vetting the below statement for grammatical mistake 'Does AMS can lead to death? ' Pls.check & help me with corrections.

Hello gullu_summi

No, I'm afraid that's not correct. 'can' is a modal auxiliary verb and so 'do' is not used in a question. The correctly formed question would be 'Can AMS lead to death?'. I'd suggest you read our Question forms page for more on this grammar.

All the best

Kirk

The LearnEnglish Team

Hi could you please help me, what to write(can or could) in the following sentence. 'I am very hungry. I can/could eat a horse'. What's the correct answer?

Hello Garry301,

The correct form is 'could' because you are talking about a hypothetical situation (I could eat a horse if you gave me one) rather than a physical ability (I can eat a horse because I've got an enormous stomach).

Peter

The LearnEnglish Team

if she is single today, i could have married her. Am i correct? means - the ga if this gal is unmarried , i can mry

Hello Ali. Chy

No, I'm afraid that's not correct. I'm not completely sure what you want to say, but 'If she is single, I could marry her' is grammatically correct and logical.

All the best

Kirk

The LearnEnglish Team

What would be the correct way of asking a teacher to meet me the next day? 1. May I meet you tomorrow, please? 2. Could we meet tomorrow, please? 3. May we meet tomorrow, please?