Possibility

We use the modal can to make general statements about what is possible:

It can be very cold in winter. (= It is sometimes very cold in winter)
You can easily lose your way in the dark. (= People often lose their way in the dark)

We use could as the past tense of can:

It could be very cold in winter. (=Sometimes it was very cold in winter.)
You could lose your way in the dark. (=People often lost their way in the dark)

We use could to show that something is possible in the future, but not certain:

If we don’t hurry we could be late. (=Perhaps/Maybe we will be late)

We use could have to show that something is/was possible now or at some time in the past:

It’s ten o’clock. They could have arrived now.
They could have arrived hours ago.

Impossibility:

We use the negative can’t or cannot to show that something is impossible:

That can’t be true.
You cannot be serious.

We use couldn’t/could not to talk about the past:

We knew it could not be true.
He was obviously joking. He could not be serious.

Ability:

We use can 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 to talk about the ability to do something at a given time in the present or future:

You can make a lot of money if you are lucky.
Help. I can’t breathe.
They can run but they can’t hide.

We use could to talk about past time:

She could speak several languages.
They couldn’t dance very well.

 

Permission:

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 if you like.
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 free.

Instructions and requests:

We use could you and 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 and invitations:

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 can give you a lift to the station.

 

Exercise

Section: 

Comments

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

In the sentences "you could say", "you could use", "it could mean", does "could" here show possibility in the present? Which could means "may be able to"?

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