The difference between may and might?

"May" has the sense of "being permitted";

e.g. the invigilator of a written examination due to commence at two o'clock would say: "The time is two o'clock; you may commence writing now", meaning "You are permitted to start"... (not "You can start writing now" of course, which means "You are able to start", but that's another issue).

"Might" has the sense of something being a possibility, either in the past, present or future.

e.g. the same invigilator, if he or she spoke good English, might say:"You might start writing now, but if you do then you will be disqualified, because it is not yet two o'clock". Not only might that same invigilator deliver that warning, but he or she may deliver it, because that is part of his/her duty - invigilators are allowed to inform examinees of correct procedure.

Furthermore, the same invigilator might say: "If you start writing before two o'clock I might come over and smack you"; it is possible that he or she is under great duress and has lost it; however, the invigilator may not say that, because no invigilator may smack examinees or threaten to do so.

And of course no well-spoken invigilator should say: "If you start writing before two o'clock I may come over and smack you", because that would be a lie - it implies he or she has permission from the Exam Board, and no Exam Board permits invigilators to smack examinees.

1. Mother: "It might rain today". Well-spoken son:"I might take an umbrella, but I lost mine, so it depends on whether I can find one or not. May I borrow yours please?"

2. Mother: "It may rain today". Well-spoken son:"Who do you think you are Mum, telling the clouds what to do? God?"