Most writers use may and might interchangeably:
I may go to the library to work on my term paper.
I might go to the library to work on my term paper.
Is there a difference? There is, but it’s slight. May suggests a possibility that an action will occur, while might suggests a slightly smaller possibility. So if I say that I may go to the library, there’s a reasonably good chance that it’s on my agenda. But if I say that I might go, the odds that I will aren’t quite as good.
The distinction between the two is sufficiently fine that it’s not something writers need to obsess about. However, when referring to something in the past, the rules get tighter. The past tense of may is might.
She might have left a message on my voice mail. (Not she may have)
From time to time, writers also struggle with the difference between may and can. The difference here is more pronounced. May expresses permission, while can expresses ability. Moms everywhere are notorious for emphasizing this particular grammatical difference.
Question: Mom, can I paint my bedroom walls black?
Answer: I’m sure you can, but you may not.
In informal speech (including dialogue in fiction), we have slipped into using can when may would be more appropriate. In truth, strict adherence to the difference between the two can seem a little prissy at times. Still, it’s a valid distinction that writers should strive to apply when it makes sense.
I would say that the difference between ‘may’ and ‘might’ is not in the level of probability but in the register. To me, ‘might’ is much more natural in informal conversation and ‘may’ sounds more formal.
There is a very important may-might distinction, widely ignored or misunderstood, that is not addressed in this article. It shows up in what I believe is the conditional subjunctive. (Please advise if I’ve got the name of mood or tense wrong.) Ex: “John may not have waited if he’d known Mary had a ride home.” The verb should be “might not have waited.” This is cringe-inducing to the sensitive ear, because it implies that it has yet to be determined whether or not John waited. Can you elaborate on this?
Thanks, MW
Corina has a good point that the use of these words may be contextual.
Would looking at other romance languages help? Do these two words use different verb tenses in say French, Spanish, Italian?
In response to Madolin’s question, the sentence you used as an example expresses both a result and a condition. Both expressions require one of the perfect verb tenses that show an action already completed. Since the actions are in the past, the auxillary verb should be in the past tense. And since “might” is the past tense of “may,” it’s the correct choice. –J. Landis
I want to be sand exercise
Both words are to express possibility, however, the context is very important. For example: if somebody said “I may dye my hair.” it would imply more that they were allowed to rather than that they were considering it. Or, for want of a better example, “I may enter this room.” I, personally, hate the use of ‘may’ in place of ‘might’ because I associate it more with its meaning ‘to express opportunity or permission’.