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.]





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,

Dear sir
Can I say (they could have arrived by now) instead of (they may have arrived by now) for (perhaps they have arrived) ??

Hello Yasser Azizi,

Yes, you can say that. There is a slight difference in meaning, as 'could have' tells us that something is not impossible, while 'perhaps' tells us that there is a genuine possibility. We could use 'could have' in an entirely hypothetical situation, unlike 'perhaps'.

For example:

Paul could have won the race. We'll have to wait and see the photo to be sure. [a real possibility]

Paul could have won the race but he was injured. [hypothetical]

Paul could have won the race. We'll have to wait and see the photo to be sure. [a real possibility]

Perhaps Paul won the race but he was injured. [incorrect]


Best wishes,


The LearnEnglish Team

Very helpful
Thank you

Dear sir,
Is this correct? if am late and want to send a message to boss
1. I will be there within an hour
2. I am on the way
or what you suggest?

Hello Umari,

Both sentences are appropriate, though 2 would be untrue if you weren't already out of your home and really already moving towards work. If I were your boss, I would probably be happier to hear 2, since it shows actual evidence, whereas 1 is just a promise.

All the best,
The LearnEnglish Team