May is used to ask for permission.
- May I come in, please?
- May I go home now?
May not is used to deny permission.
- ‘May I go now?’ ‘No, you may not.’
Notes
Nowadays, the denial of permission is often expressed by cannot. This usage is probably encouraged by the fact that the contraction can’t is easier to pronounce than the contraction mayn’t.
- May we go out, Mummy?
- No, you can’t. OR No, you mayn’t.
Possibility
May can be used to express possibility.
- She may come.
- The prices may fall soon.
- He may get upset if you don’t talk to him.
In wishes
May is used in expressing a wish.
- May God bless you!
- May his soul rest in peace!
In subordinate clauses
May is used in subordinate clauses that express purpose.
- Work hard that you may get good marks.
- We eat that we may live.
Might
Might is the past tense of may in indirect speech.
- He said, ‘I may win the first rank.’
- He said that he might win the first rank.
- The boy said, ‘I may have said so.’
- The boy said that he might have said so.
Notes:
Might indicates less possibility than may.
- I may pass. (perhaps 50% chance)
- I might pass. (perhaps 20% chance)
- He may recover. (He has good chances of recovery.)
- He might recover. (Less probable)
Might is also used when you want to sound extremely polite.
- If I might make a suggestion, couldn’t we stop this discussion now?