'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.

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Average

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.

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

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

Hello Mison,

It's fine to use 'could' in that way. Well done!

Peter

The LearnEnglish Team

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

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

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

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

Hi smit,

In this example, could doesn't work. Could is for a past ability (not present ability). Could can mean possibility in the present, but speaking English is an ability, not a possibility.

If I'm not 100% sure, I would say: She might be able to. (Might shows a lack of certainty.)

Best wishes,

Jonathan

The LearnEnglish Team

Hi English Team, Hope you are doing well. I have a few Qs 1. There are three possibilities: we can talk to a lawyer, we can go to the police, or we can forget all about it (How about 'could'?) 2. What shall we do? We can try asking Lucy for help (How about 'could') 3. What shall we do tomorrow? Well, we could go fishing (How about 'can') 4. This success could not have been achieved without your cooperation. (How about 'cannot have') Thanks so much.

Hello IsabelTim_123,

In 1 and 2, 'could' is also possible and I'd understand it to mean the same thing. In 3, there is nothing grammatically wrong with saying 'can', but it's not really an appropriate response to the question. The question asks for ideas and usually we use a hypothetical form like 'could' to answer such a question, not a form that speaks about ability. In 4, 'cannot have' is not correct because the sentence is speaking about an unreal past, i.e. a past condition that didn't really exist. 'cannot have' makes a statement about a real past action which we think did not occur.

All the best,

Kirk

The LearnEnglish Team

Children of divorced parents may have difficulty in forming stable relationships - How about Can? After having a baby, a woman may suffer from depression for several months - How about can? During the autumn, many rare birds may inhabit on the rocky northern coasts of the island. - How about can? The rash could be a symptom of something more serious - I saw this example in a grammar book. It says it means "maybe it is a symptom". But isn't it a general possibility (i.e. it sometimes happens)? In other words, could I use can or may instead? Thanks a lot English Team

Hello Anisha00329,

Yes, you could use 'can' is all three of those sentences to mean the same thing.

As for the sentences about a rash, both 'can' or 'may' are also possible here if you're speaking about a general possibility, but 'could' is also fine if, for example, you're a concerned parent looking at the rash and deciding whether to take that person to the hospital.

All the best,

Kirk

The LearnEnglish Team

Hello there! Namastey! I have been looking for tense structures with modals. For example, we can have the following tense structures for the modal "Must" as in: 1. They must ask. (Simple) 2. They must be asking. (Progressive) 3. They must have asked. (Perfect) 4. They must have been asking. (Perfect Progressive) So, my question is do we have these structures for the modals "can", "dare", "need", "used to", "have to" and "ought to"? I will be grateful to your priceless assistance! Thank you! Deepak Kumar Teacher of English

Hello dkbc,

Those forms are possible for all full modals; verbs like need and dare are not always treated as modal verbs, and in fact are slowly transitioning to being normal verbs rather than modal verbs. Verbs like have to and ought to are, at best, semi-modals, and used to is generally described as a marginal modal.

For some modals it's hard to imagine a context in which they would be used because of the particular meaning of the verb. For example, while can have done is a possible form, it is very hard to imagine a context in which it would be used naturally.

Peter

The LearnEnglish Team

Hi teachers, could you please help me? I find a number of sentences confusing: First - Failure to produce proof of identity could result in prosecution. I am confused why could is used. Are may, might, and can possible alternatives? Second - Whether the company could continue to use the services has been up in the air since the ban came into effect two weeks ago. Is 'can continue' possible? Third - Could you turn your chairs to face this way? Could "would you..." be used here? I appreciate your help teachers!

Hi Lucas_xpp,

In your first sentence, could is used to show possibility. You could replace it with may or might but not with can, which would show ability, not possibility.

In your second example, could is used to show past ability. You could use can here, but it would change the meaning to present ability. Given that the situation is still unresolved, can works fine here.

In your third example, you could use would. Both could and would can be used in this type of polite request.

Peter

The LearnEnglish Team

We could not pause the job losses indefinitely — it was always a question of ‘not if, but when’ This is an announcement by a company of job cuts. Why is "could" used instead of "can"? in every sense of the word means In every way in which something could be interpreted or understood. Why is "could" used instead of "can"? Thanks a lot teachers.

Hi Anisha00329,

In the first sentence, could not shows inability in the past. You might argue that the situation (cutting jobs) is a present situation, not a past one. But by using the past form could not, the speaker frames it as a past action. It may be referring to the time that the job cuts were decided (which is a time before the current announcement, i.e. a past time).

In the second sentence, could is used to show hypothetical possibilities, not real ones. It's not claiming that this thing actually is or can be interpreted or understood in all these ways in reality.

Best wishes,

Jonathan

The LearnEnglish Team

1) This was the best room we could get at such short notice. - Would it be better to say "we were able to get"? 2) A course is an action or series of actions that you could take in order to deal with a particular situation - Would it be better to say "you can take"? 3) the question for the next six months is the extent to which those countries opposed to the world being divided can prevail - Since this refers to a future event, why is "can" used instead of "could"? Thanks a lot English Team.

Hi AsahiYo20,

I'll try to answer your questions in turn.

Both could and were able to are possible in this sentence. Were able to is often used to show ability on a particular occasion (see here for more explanation and examples). But That was the best I could do (and variations) is a very common phrase too.
You can use can or could, but the meaning is slightly different. Can presents 'taking action' as a realistic possibility for the listener. Could presents it as an imagined or hypothetical situation.
We can use can to talk about the ability to do something at a future time. For example: I can go on holiday next month.

Does that make sense?

Best wishes,

Jonathan

The LearnEnglish Team

You gave everything you can throughout. Is it a complusion that "could" should be used instead of using "can" Would be really grateful if someone responds to the query. Thank you :)

Hello Sharath.v,

It's hard to be absulutely certain without knowing the context, but I think could is necessary here because the whole sentence is in the past, as shown by the past tense verb gave.

Peter

The LearnEnglish Team

1) He couldn’t be a doctor. He isn’t wearing a white coat This sentence seems to be about present impossibility. I think only "cannot" can be used to express such meaning. But why is "couldn't" used here instead? 2) It might/could be described as an act of provocation. Could I use may/can instead? Grateful if you could help.

Hello Najmiii3579,

Your first sentence looks rather odd to me. I think the normal form would be either [can't be > isn't wearing] for present meaning or [couldn't be > wasn't wearing] for past.

With your second sentence, it's difficult to say for sure without knowing the context and intention of the speaker. A word might be possible in theory, but change the meaning in such a way that it is highly unlikely, and we would have to describe each context in detail to explain.

If you can tell us what you want to say (i.e. what meaning you want to convey) then we'll be happy to help you to do so.

Peter

The LearnEnglish Team

Sir, I have two questions. Grateful if you could help. 1st Sentence: "He has every attribute you could want and could play for any team." Could I use "may" or "can" instead of can? 2nd Sentence: "The earliest we can finish is next Friday." Could I use "can" or "may" instead?

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.

Peter

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,

Kirk

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.

Peter

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,

Jonathan

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,

Jonathan

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.

Hi AsahiYo20,

Can works fine in each sentence. However, the use is different in each example. The first sentence uses can to express possibility. The second uses can to express ability. This affects whether or not could can be used.

Even though if is not used, the first sentence is a form of conditional, expressing a condition and a dependent result. Could would make the sentences hypothetical and would require changes in the first clause:

A compromise would have to be reached between all the powerful vested interests before any restoration work in the city could take place.

[the speaker thinks the situation is unlikely]

In the second sentence, could would have a past meaning (past ability), and so the verb in the first clause would also need to be past:

I liaised with end-users, resellers and partners to see how we could improve our portfolio of products and services.

Peter

The LearnEnglish Team

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.

'can' and 'could'

Possibility and impossibility

Ability

Permission

Requests

Offers

Suggestions

Questions and negatives

Online courses