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Chances: may, might and could

You may be right; We may go climbing.​

We often use may, might and could to talk about the chance (possibility) that something will happen, or is happening.

  • We may go climbing in the Alps next summer.
  • ‘I think Labour are going to win.’ ‘You may be right.’
  • Daniel might phone. If he does, ask him to ring later.
  • ‘Where’s Emma?’ ‘I don’t know. She might be out running, I suppose.’
  • They’ve agreed, but they could change their minds.

May well, might well and could well suggest stronger possibilities.

  • ‘I think it’s going to rain.’ ‘You may well be right – the sky’s really black.’

Can is not normally used to talk about the chance that something will happen or is happening.

  • not It can rain this afternoon.
  • not Emma can be out running.

may, might and could: the difference​

Might and could are not often used as past forms of may and can: more often they are used to talk about the present or future. Might and could are less definite or more hesitant than may, suggesting a smaller chance – they are used when people think something is possible but not very likely. Compare:

  • I may go to London tomorrow. (perhaps a 50% chance)
  • Joe might come with me. (perhaps a 30% chance)

Questions: may not used​

May is not normally used to ask about the chance of something happening.

  • Are you likely to go camping this summer? (not May you go camping …?)
  • Has Emma gone running, I wonder? (not May Emma have gone running?)

But may is possible in indirect questions (for example after Do you think).

  • Do you think you may go camping this summer?

Might can be used in direct questions, but this is rather formal.

  • Might you go camping? (less natural than Do you think you may/might …?)

Two negatives: may/might not and can’t​

There are two ways to make may/might negative: with may/might not (= It is possible that … not …) and with can’t (= It is not possible that …). Compare:

  • She may be at home. (= Perhaps she is at home.)
    She may not be at home. (= Perhaps she is not at home.)
    She can’t be at home. (= She is certainly not at home.)
  • You might win. (= Perhaps you will win.)
    You might not win. (= Perhaps you won’t win.)
    You can’t win. (= You certainly won’t win.)

Couldn’t is possible with the same meaning as can’t, but is less common.

might meaning ‘would perhaps’​

Might and could (but not may) can have a conditional meaning (= would perhaps).

  • Don’t play with knives. You might/could get hurt. (= Perhaps you would get hurt.)
  • If you went to bed for an hour, you might feel better. (= … perhaps you would feel better.)

Indirect speech: might/could​

Might/could is used in past indirect speech when may was used in direct speech.

  • ‘I may go to Scotland.’ ‘What?’ ‘I said I might go to Scotland.’

Past: might/could + infinitive not used​

Might/could + infinitive is not normally used to talk about past possibility (except in indirect speech).

  • I felt very hot and tired. Perhaps I was ill. (not … I might be ill.)
  • but I thought I might be ill.

may/might/could have …: She may have missed her train.​

However, to say that it is possible that something happened or was true in the past, we can use may/might/could have + past participle.

  • ‘Polly’s very late.’ ‘She may have missed her train.’ (= It is possible that she missed …)
  • ‘What was that noise?’ ‘It might/could have been a cat.’

May/might have … can sometimes refer to the present or future.

  • I’ll try phoning him, but he may have gone out by now.
  • By the end of this year I might have saved some money.

might/could have …: You might/could have killed yourself.​

To say that something was possible but did not happen, we can use might/could have …

  • You were stupid to try climbing up there. You might/could have killed yourself.
  • If she hadn’t been so bad-tempered, I might/could have married her.

May have … is now sometimes used with this meaning too; some people feel that this is not correct.

  • You were stupid to try climbing up there. You may have killed yourself. (More normal: … You might/could have killed yourself.)
note

For might/could have … used to criticise people for not doing things, (see here).

The difference between may/might/could and should/ought to​

We use should and ought to to express a deduction that something is probable: they suggest that we have a good reason for this belief.

May, might and could simply say that something is possible, without suggesting that we have a good reason for thinking it is true or will happen. Compare:

  • Anna should be in the office now – it’s ten o’clock.
    Dan may be in the office now – I don’t know what time he starts work.
  • I’ve got all John’s keys here. One of them ought to open the safe.
    Let’s ask Amy. She might know which is the right one. It’s worth a try.