Questions and negatives:

We make questions by putting the subject after may/might:
May I …? Could I … Might I …? Etc.

The negative forms are may not and might not..

We use may:

  • when we are not sure about something:

Jack may be coming to see us tomorrow.
Oh dear! It’s half past ten. We may be late for the meeting.
There may not be very many people there.

  • to make polite requests:

May I borrow the car tomorrow?
May we come a bit later?

When we use may not for a refusal it is emphatic:

You may not!
You may not borrow the car until you can be more careful with it.

We use might:

• when we are not sure about something:

I might see you tomorrow.
It looks nice, but it might be very expensive.
It’s quite bright. It might not rain today.

• As the past tense of may for requests:

He asked if he might borrow the car.
They wanted to know if they might come later.

• For very polite requests:

Might I ask you a question?
Might we just interrupt for a moment?

We use may have and might have to show that something has possibly happened now or happened at some time in the past:

It’s ten o’clock. They might have arrived now.[= Perhaps they have arrived]
They may have arrived hours ago. [= Perhaps they arrived hours ago.]




Hi The Crew and all the other friends,
I want to make some comments on modal expressions may/might/could have + v3 , also I want to ask you some examples. It would be very kind of you if I might get answer or a reply from you, thanks beforehand...

First of all I should say that I have been working as an english language teacher and trainning english language classes. I teach my students that
may have done/might have done and could have done have got a same meaning while mentioning a past possibility at a degree of % 50 certainity .

as an example
A: I cannot find my keys, where can they be?
B: I do not know exactly but you may/might/ could have dropped them in the car.
You may/might/could be right, let's check .

Are these three options correct ?

Also i teach my students that 'could have done' has another meaning in the past that means ' i had the chance or oppurtunity to do something in the past but i didn't do'
as an example
'Yesterday it was my day off so i could have gone to cinema but i chose to stay at home and slept all the day.'

Also i desire to write a sentence and want to get your oppinion about it

'By the end of this month, we may/might/could have sold half of the tickets.'

What's your oppinion about the sentence? Are the three options can be used interchangeably or are there any differences in meaning?

Thank you

Hello BlackNoah'sSon,

All three options (may, might and could) are possible in your example and have the meaning 'it is possible that this happened'.

As you say, 'could have' can also mean 'had the possibility but did not'.

I think all three options are possible in your last example. There is an implied condition here, I think, along the lines of 'if everything goes well then...' or 'if we work hard then...'



The LearnEnglish Team

Thank you Peter for your confirmation and clarification,

In order to leave a useful note for future search, I also want to point out another usage of 'might have done' which has meaning difference with 'may have done'. I mean these two modal patterns do not always have the same meaning.

'' Why did you do that madness with your car!? We might have had a car accident.''

I think in this context we cannot use 'may have had a car accident',

What do you think about this case?

Hello BlackNoah'sSon,

In many contexts might have and may have are interchangeable. However, there is one context in which there is a clear difference.

If we do not know whether or not something is true, we can use either form:

He may have gone to the meeting. You'll have to check.

He might have gone to the meeting. You'll have to check.


However, if we know something is not true, then we use might have and not may have:

He might have gone to the meeting if he hadn't been sick.


Your example is similar to this. The people in your example did not have an accident, so might have is the only possible form.




The LearnEnglish Team

Thanks Peter

Hello The LearnEnglish Team,

I once encountered sentences in a grammar book as follows,
"It's a pity you weren't here! You {might have] been able to help Dad, with your interest in holistic medicine. You [could have] given him some of your aromatherapy treatments."
What is the difference between modal verbs in the second and the third sentence?
I think both "could have" and "might have" are used to express uncertainty in the past, but "might have" tends to refer to past possibility which did not happen.
In this case, I think both events in these two sentences are hypothetical since they didn't happen. Then why can't I use "might have" for both sentences?

Thank you in advanced,

Hello toandue,

The difference is as follows:


  • might have tells us that helping was a possibility/something was not impossible. In this case, we mean that there was a chance of something helping.
  • could have tells us that you had the opportunity/you had this option. In this case, we mean that it was possible to give the treatments.


As you say, both describe hypothetical situations as the person in question was not there (it's a pity you weren't there), but there is a difference in meaning.



The LearnEnglish Team


Don't know if you feel this is an appropriate venue for this question, but I am an freelance editor in the US who edits a lot of English and Australian authors, and I have noticed a tendency for these authors to use "may" in sentences referring to the past such as this:

If John had followed in his father's footsteps, they may have gotten along better as adults.

To my American English ears, I would expect it to be:
If John had followed in his father's footsteps, they MIGHT have gotten along better as adults.

That is to say, use "may" for present-tense sentences and "might" for past-tense ones.

When I first started encountering this phenomenon in manuscripts, I was correcting what I thought was the occasional mistake by an author, but then I noticed it was only happening with Brits and Aussies. Are they using "may" correctly (as in the first example) according to the rules of British English? Or am I just completely wrong?

Hello MichelleA,


There is a difference between US English and UK English here, certainly. The first sentence is quite correct in UK English as we (I am from the UK) use 'may' and 'might' interchangeably to a much greater extent than US English speakers.


This is an area of change, I believe, and the distinction between 'may' and 'might' is slowly disappearing. There is still a vestigial sense of 'might' for past reference when used in requests (see the examples on the page above) and in the use of 'might' for counterfactuals (reflecting the use of past forms for hypothetical meaning). Again, see the examples above for this.


Best wishes,


The LearnEnglish Team

Thank you, Peter, for the prompt reply. The mystery is solved! That was very helpful.

Take care,