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.

Probability 1


Probability 2


Probability 3


Probability 4


Probability 5




Hi, Kirk,
Thanks for your reply.
They could have arrived hours ago.
I mean that if this sentence refers to a possibility of their arrival but in the past tense or it means that all the situation is hypothetical as they didn't go somewhere to arrive, but they could have arrived if they left.
I hope it's clearer now.

Hello Inas,

Thanks for clarifying that. Yes, it could be used in both of those ways.

All the best,
The LearnEnglish Team

Hi, Kirk,
It’s ten o’clock. They might have arrived now.
Could this sentence used in the same both ways??

Hello Inas,

You could use it in both ways, though if you wanted to communicate the hypothetical meaning, you'd have to clarify this in the context for this hypothetical meaning to come across.

All the best,
The LearnEnglish Team

what is the difference between i might come and i might not come? when should i use might not?

Hello hikaru tsuki,

Which of these you use depends on what you consider the current, normal or likely state. For example, if I say 'I might come' then I am suggesting or assuming that the normal situation is not coming, and I am saying that there is a chance of this changing.

As another example, if I look out of the window and say 'It might rain' then I am suggesting that the normal/expect weather is dry, but that rain has become a possiblility.


Best wishes,


The LearnEnglish Team

Hello, teachers.
I wander if this sentence correct, I mean the use of (might not) to talk about an impossible situation in the past?
Here is the sentence (They lost the game yesterday. They might not have played well.)??

Hello Karzan,

You can use 'might not' with 'have played' to speculate about the past, but I wouldn't call that an impossible situation. By the way, another way to speculate about why they lost is: 'Perhaps they didn't play well'.

Best wishes,
The LearnEnglish Team

Please, can someone tell me which one of these is correct:
1) May John keep doing the task....
2) May John keeps doing the task...

Hello Adediran,

The first sentence is correct, though it is not a particularly natural or likely sentence.

After modal verbs such as 'may' we use the base form of the verb, without the third-person 's'.

Best wishes,


The LearnEnglish Team