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Level: beginner


We use may, might and could to say that something is possible, but not certain:

They may come by car. (= Maybe they will come by car.)
They might be at home. (= Maybe they are at home.)
If we don't hurry, we could be late. (= Maybe we will be late.)

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.)

Be careful!

We do not use can to talk about specific events:

A: Where's John?
B: I'm not sure. He may/might/could be 
(NOT can) in his office.

Notice the difference in meaning between can and may/might/could:

That dog can be dangerous.
(= Sometimes that dog is dangerous. I know.)

That dog may/might/could be dangerous.
(= Perhaps that dog is dangerous. I don't know.)

can and may/might/could


Level: intermediate

We use may have, might have or could have to make guesses about the past:

I haven't received your letter. It may have got lost in the post.
It's ten o'clock. They might 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.)

could and could have



Level: beginner

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 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.


Level: beginner

We use must to show we are sure something is 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 should to suggest something is true and we have reasons for our suggestion:

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

Level: intermediate

We use must have and should 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.
It's nearly eleven o'clock. They should have arrived by now.

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Hello Knightrider,

I think that's a good summary. The communicative meaning of the phrase is very much dependent on the context, so it's important to look at how it is used in context, not in isolation.


Best wishes,


The LearnEnglish Team

Hello Peter,

Yes absolutely. Context is all-important to distinguish the two meanings. I just wanted to be sure that I have grasped both senses. Thanks again


How can you differentiate between ability, possibility, probability and obligation in the sentence below?
´´Every person has particular ways to do things that may seem strange to others´´.
Thank you!

Hello girlbah,

One way you could do it is by using other words or phrases instead of 'may'. For example, 'be able to' for ability, 'it is possible' for possibility, 'it is likely' for probability and 'must' or 'should' for obligation.

Which one makes the most sense to you here?

All the best,
The LearnEnglish Team

Whats the meanning of "vicious dog"?

Hello Wolframio,

The phrase is 'a pretty vicious dog'. 'Pretty' here means 'quite' or 'fairly'.

You can find the meaning of 'vicious' in any online dictionary - see here, for example.


Best wishes,


The LearnEnglish Team

Good day !

what tense is `must have been´ ?

Hello mgfielrocha,

In 'must have been', 'have been' is a perfect infinitive, which in this case is used to speak about the past, but as far as I know there is no name for the tense in this form. This is because 'must' and most modals don't really have tenses -- we have to use other words to express the same idea in a different time. For example, to speak about past obligation, we have to use 'had to' instead of 'must'.

If you're interested in learning more about this, the Wikipedia English modal verbs page would be a good place to start.

All the best,
The LearnEnglish Team

Hi sir, can we use 'could' to make a statement in the future? E.g; I could have been driving home before she arrives on Monday.

Hi judeee,

You can use 'could' with future reference, but not 'could have'.



Best wishes,


The LearnEnglish Team