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'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.


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]


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.


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?


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.


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 ...?
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 cms10,

In the first sentence, both may and can are possibly alternatives to could in terms of grammar, but they change the meaning. May would tell us that the persion is allowed to play - not prohibited. Can woud be more similar to could but would make the situation more real. If we use could then the situation is hypothetical. If we use can then it suggests that he has a real possibility of playing for any team - he has offers and can choose amongst them, for example. For this reason, could is preferable in this context.


The meanings would be the same in the second sentence: may would describe what is allowed (by the rules, for example); can would describe what is possible and likely or realistic; could would describe what is hypothetically or theoretically possible.



The LearnEnglish Team

Hi Sir,

Thanks so much for your reply. Regarding Sentence 2: "The earliest we can finish is next Friday." I am quite confused about why "can" can be used, as this sentence is talking about a future possibility. I have been taught that "can" cannot be used to talk about a future possibility. Instead, we should use "may" or "might" or "could".

So could I say if I use "may" here, it can convey a sense of future possibility rather than what is allowed?

And also, could I say if I use "could" here, it wouldn't convey a hypothetical possibility, but a future possibility?

Thank you so much English Team.

Hello cms10,

As I see it, in this sentence, 'can' is used to speak about ability -- if I replace 'can' with 'are able to', the sentence still works. The phrase 'the earliest' somehow makes it clear that the sentence is not about a possibility, but rather is more like a prediction or even promise.

To convey the idea of a possibility you're not certain about, you could use 'may', 'might' or 'could': 'We might/could/may finish it next Friday'. Notice that it doesn't work to use the phrase 'the earliest' here.

Hope this helps.

All the best,


The LearnEnglish Team

Hope you are doing well teachers!

I read this sentence from a grammar book: The jury and witnesses were removed from the court so that they might not hear the arguments of the lawyers. The book says: "should not hear (BrE)" and "not hear (AmE)" could be used instead. May I ask whether I could use "could not hear" here?

Hello PabloTT,

Yes, you could use 'could not hear'.

To be honest, I think the best phrase here would be 'would not hear' because it expresses the intention of the person (presumably the judge) making the decision.



The LearnEnglish Team

"If we offer you the post, when can you start?"

Could I say "when could you start" or "when may/might you start" instead?

Thanks teachers!

Hi MarciaBT,

Yes! When could you start? also works fine.

The versions with may or might are possible, but less common.

  • May often means permission, so When may you start? has a more specific meaning: 'When do you have permission to start?'. 
  • The version with might means there is more uncertainty about when the person can start. It invites the person to give a tentative answer (while the versions with can and could invite a more definite answer).

Does that make sense?

Best wishes,


The LearnEnglish Team

Thanks for your reply Sir.

Would "could" convey an extra sense of politeness and be better than "can" here?

Hi MarciaBT,

No problem. Yes, could shows more politeness. Since a job interview is often the first time that the people have met, that's definitely the option I would choose.

Best wishes,


The LearnEnglish Team

Hi teacher. Hope you are doing well! This is the first time that I have posted comments here. I find this page really useful. May I ask why "can" rather than "could" or "may" is used in the sentences below? I have a feeling that since the sentences refer to some future action, "could" or "may" would be a better choice. Please correct me if I am wrong. Thanks!

1. A compromise has to be reached between all the powerful vested interests before any restoration work in the city can take place.
2. I liaise with end-users, resellers and partners to see how we can improve our portfolio of products and services.