The modal verbs are can, could, may, might, mustshall, should, will and would.

The modals are used to show that we believe something is certain, probable or possible:

Possibility:

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

They might come later. (= Perhaps/Maybe they will come later.)
They may come by car. (= Perhaps/Maybe they will come by car.)
If we don’t hurry we could be late. (= Perhaps/Maybe we will be late)

We use could have, might have and may have to show that something was possible now or at some time in the past:

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

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 the modal 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)

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.

Probability:

We use the modal must to show we are sure something to be true and we have reasons for our belief:

It’s getting dark. It must be quite late.
You haven’t eaten all day. You must be hungry.

We use must have for the past:

They hadn’t eaten all day. They must have been hungry.
You look happy. You must have heard the good news.

We use the modal should to suggest that something is true or will be true in the future, and to show you have reasons for your suggestion:

Ask Miranda. She should know.
It's nearly six o'clock. They should arrive soon.

We use should have to talk about the past:

It's nearly eleven o'clock. They should have arrived by now.

Exercise

Comments

Hi,
A-do you remember me?
B-how could I forget you?
In the second sentence 'could' is used for ability or possibility and which time it refers (present/past/future). Please explain?

Hi jitu_jaga,

I think we've already provided a lot of explanations on this point and can't really continue explaining the same point with yet more examples. Why don't you tell us what you think the meaning is here and we will comment on your idea?

The important thing is not which label (possibility/ability etc) you put on a word, but rather that you understand how it is used in communication.

 

Peter

The LearnEnglish Team

Hi,
1.How could you do that to me? Here, in this sentence 'could' is used for ability or possibility? and which time does this sentence refer(present/past/future)?
2. What is the difference between possibility and probability?

Hi jitu_jaga,

It's difficult to say for sure without context, but it looks to me as if 'could' is being used to express past, or perhaps hypothetical, ability in the sentence you ask about. If I found out that a close friend of mine planned to borrow my car without asking my permission, for example, I might say something like this. The idea is that a good friend wouldn't be able to hurt me in that way.

'possibility' refers to whether something could happen or not; 'probability' refers to how likely it is that it could happen -- it's like the level of possibility of something. The lottery is a classic example -- it's not probable that you win the lottery, but it is possible.

All the best,
Kirk
The LearnEnglish Team

Thank you Kirk. Have a nice day.

Hi,
They could come by car
They might come by car
They may come by car

Can you please explain me which of the above sentence is correct/more accurate or can be used interchangeably?

Hello QaaZee,

All of these are grammatically correct and they can all mean that there is a chance that they will come by car. Other meanings are possible for some of the examples. 'May' could refer to permission, for example, as in it is OK for them to come by car, but that would depend on the context.

 

Peter

The LearnEnglish Team

Thanks Peter,
Could you please provide an example with context for 'May' to further elaborate its use for permission.
Thank you once again.

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