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

Hello sarab,

It's not possible to be certain without knowing the context in which the sentence appears. It is probably best described as possibility ('this is an option for you') and the use of 'as...' here suggests it has  the communicative function of making a suggestion ('why not do this?').

 

Best wishes,

Peter

The LearnEnglish Team

Hello sir
in the following sentences what is more appropriate?
1. We 'can/ could' easily meet next Saturday.
2. You 'can/ could' come home at the weekend.
Sir both the examples suggest future and could is used for 'ability in past' but again we also use 'could' for giving suggestions so which modal should be used? Or can either ones be used interchangeably?

Hello amrita_enakshi,

Generally speaking, 'can' suggests that something is possible, while 'could' is more likely as a suggestion. However, context and intention is key. It is possible to use 'can' to make a suggestion like this, for example, if the context and tone of voice is appropriate.

 

Best wishes,

Peter

The LearnEnglish Team

Hi Peter

Which of these two statements is correct
-Could you me make ...
-Could you me to make ...

using base form or infinity form after can or could is confused me

Thanks

Hello masri.ahm04,

I'm afraid neither of these is correct -- 'me' should come after the verb 'make'. The bare infinitive form is used after modal verbs like 'could', so the correct way to say this is 'Could you make me ...'

All the best,
Kirk
The LearnEnglish Team

Thanks a lot Kirk, I got it.
So I can say that 'could you make me to make .....'

Hi Peter
What is the deference between tow following sentences
-It can be used as ...
-It can be using as ...
In another words, when I should use past participle and ing-form, in this case they are an adjective, aren't it ??

Thanks a lot.

Hello masri.ahm04,

The first option ('it can be used as') is fine. The second option is not correct grammatically.

In these phrases 'used' is not an adjective but a past participle of the verb 'use'. It is a passive construction:

He uses the stick as a sword. [active]

The stick is used by him as a sword. [passive]

 

Your examples have a modal verb ('can') and so there is an infinitive form:

He can use the stick as a sword. [active]

The stick can be used by him as a sword. [passive]

 

You cannot replace the past participle ('used') with a present participle ('using') in passive constructions.

 

Best wishes,

Peter

The LearnEnglish Team

Hi. Team
In the (can or could) you mentioned for permission could is more formal and polite
Ex. Could I ask a aquestion?
But in May or Might section you said (might) is very polite for request
Ex. Might I ask aquestion?
My question is what is the diffrence between these two sentences.
Coud Iask a question?permission
Might l ask a question?request
I think they have the same meaning. Why they are different in your explanation? Thanks alot.

Hello Helan gian,

The meaning is the same - a polite request. 'Might' is more polite and less common than 'could' - that is the difference between the two. 'Might' in this use is rather old-fashioned and quite unusual, I would say.

 

Best wishes,

Peter

The LearnEnglish

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