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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.

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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Comments

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

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