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,I'm a new member, This site is very good and useful for me
thanks a lot  

Hi! well my question is this, Can we use Must not instead of Can not or Could Not
for impossible actions.

Hello Farrukh!
Grammatically, you can, but mustn't with this meaning is uncommon these days. Generally, we use can't.

Hope that helps!
Jeremy Bee
The LearnEnglish Team

Hello, and thank you for your great grammar service.
I am confused by these examples:
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)

I thought that "could" is used for conditionals. I mean that what I read above is that every winter can be very cold (not just in the past), and that I can lose my way in the dark even in the future. Am I totally wrong?
Thank you for your attention.
Daniele Giacomini

Hello dg7!
These sentences are both past. For example, in Europe in the 17th and 18th century, there was a "mini ice age" when the weather was unusually cold.
Back then, it could be very cold in winter.
Likewise, for the second sentence:
In the past, there were no electric street lights. You could lose your way in the dark.

That's all - it's difficult to understand without the context of the sentences, but you can use this structure to talk about the past.
Jeremy Bee
The LearnEnglish Team

i'm  new member please any body  could me?

Hello everyone...
I'm newcomer here. I hope I can improve my english by joining this site. I'd like to make friend too... ^_^

I'm very confused about modal verbs , I don't know how to choose the proper one
It is very confused subject .

when we use "founded" word.

I can't get meaning of following sentences-
We knew it could not be true.
He was obviously joking. He could not be serious.
Please help me overcome
Thanks a lot