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

Section: 

Comments

Hello,
I'm a little confused about some forms of modal verbs: you say that we use the negative "couldn't" to show that something was impossible, however, some books say that for impossibility in the past we should use "can't have" or "couldn't have" (for ex. Sarah hasn't contacted me. She can't have got my message.) So, where's the truth? Thank you a lot

Hello elena24,

You are confusing two different uses here. The first is the modal 'couldn't', which can describe past impossibility:

He couldn't swim when he was six.

I couldn't stop playing the game.

We cannot substitute 'can't have' here.

The second form is the perfect modal 'can't have', which is used when we are deducing somether from evidence. It shows our belief or inference about a situation, not a fact about the past. For example, in your sentence above the speaking is deducing that Sarah can't have got the message because she has not been in touch - a logical deduction from evidence. In this use both 'couldn't have' and 'can't have' are possible.

Best wishes,

Peter

The LearnEnglish Team

 

which modal should be used in the following statement? Please give reasons as well
You_____ do your work properly.
i think so it should be 'should'

Hello meena1234,

Almost any modal verb can be used in this sentence: will, can, should, could, might, may, won't, can't, must etc. Without a context it is impossible to say which is needed.

Best wishes,

Peter

The LearnEnglish Team

Good morning!

Reading this article, I find myself a little surprised as I always assumed a different pattern of usage for "may", "might" and "might have" because I basically would tend to think about how a sentence sounds more than how much it adheres to grammar rules. I know it's a bad, bad habit and that's why I tend to come to the basics from time to time, although being in the upper-intermediate/advanced level. This is most likely a wrong mindset coming from (another) bad habit of trying to search a direct translation of tenses between my native language and English so a big THANK YOU for this great article.

Hey there
so I'd like asking
what is the difference between those sentencesq
could be very cold in winter.
It can be very cold in winter.
and please point out any mistakes in the question text
thanks.

Hello abdullah,

You can find an explanation of 'can' and 'could' on our can, could and could have page, and be sure to look at the other pages in the Modal verbs section as well.

Best regards,
Kirk
The LearnEnglish Team

Hello,

I need your help in understanding the difference between "must" and "will" when we want to express a deduction. What's the difference between them? Is one stronger than the other? Are they used to express different nuances?

For example: The phone's ringing. That must be Dad...or that'll be dad?

Thank you for your insights.

Hello Knightrider,

The difference is quite subtle. We generally use 'must' when we are making a logical deduction which has a strong basis. For example, we would say 'That must be Dad' if we had been waiting for a phone call from Dad for a while and it was overdue. We would use 'will', on the other hand, for something that is normal, expected or typical. For example, we would say 'That will be Dad' if the phone rings and we know that Dad always phones at this time on this day. In other words, 'must' expresses a logical deduction based on some kind of evidence, whereas 'will' expresses an expectation based on the normal pattern of things.

Of course, these are subjective assessments rather than objective rules of what is correct and what is incorrect. This means that a given speaker can choose which form is most appropriate for a given situation, depending on how they see that situation.

I hope that helps to clarify it for you.

Best wishes,

 

Peter

The LearnEnglish Team

A thorough illustration, as always. Now I got it. Thank you so much Peter.

Regards.

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