May and might are two commonly confused modal verbs in English. Both are used to express possibility, permission, and formality, but they are not always interchangeable. Each verb carries a different level of certainty and tone, which affects meaning in real communication.
May vs. Might
Key Differences at a Glance
| Usage | May | Might |
|---|---|---|
| Possibility | More likely, based on real evidence | Less likely, uncertain or hypothetical |
| Permission | Standard and formal | Very formal and hesitant |
| Wishes | Correct form | Not used |
| Reported Speech | Changes to might | Used as past form of may |
Possibility
May is used when something is reasonably possible or supported by evidence.
Might is used when the possibility is weaker, more uncertain, or imaginary.
- The weather may improve later today.
- If I won the lottery, I might buy a boat.
Permission & Requests
May is the most common choice for polite or formal permission.
Might sounds more distant and cautious and is less common in everyday conversation.
- May I come in and wait?
- May I use your phone?
- Might I suggest a different approach?
Wishes
When expressing a wish or hope, only “may” is used.
- May you have a happy birthday!
- May the best team win!
Reported Speech
In reported speech, may normally changes to might.
- Direct: “I may be late,” he said.
- Indirect: He said he might be late.
May Not vs. Might Not
May not is often used to refuse permission.
Might not is used to express the possibility that something will not happen.
- You may not go out tonight.
- It might not rain this afternoon.
When to Use May vs. Might
May
- Used for realistic or supported possibilities.
- Used for polite or formal permission.
- Used for wishes and hopes.
- We may go to the beach tomorrow.
- You may leave early if you finish your work.
- May you have a wonderful day.
Might
- Used for weaker or less certain possibilities.
- Used in hypothetical or conditional situations.
- Used as the reported (past) form of may.
- She might be running late.
- If it rains, we might cancel the picnic.
- He said he might arrive late.
Comparison Pairs: May vs. Might
- I may go to the party.
- I might go to the party.
- She may have forgotten her keys.
- She might have forgotten her keys.
- May I borrow your pen?
- Might I trouble you for a moment?
Last Updated on January 19, 2026
I think that your description of may/might in relation to “Possibility” is confused. Both “may” and “might” express what is possibly factual with minimal nuances. They can be and are used interchangeably.
e.g. “He may come but he may not.” is interchangeable with “He might come but he might not.” To a very experienced user of English “might” possibly contains a hint that the event is more related to a personal choice, but this distinction is so subtle that learners of English can ignore it.
As for “might” being used to express what is counterfactual, I fail to see how this makes much sense. Both “may” and “might” always refer to events which are possibly factual, but not “counterfactual” (If I am wrong, I would be keen to see an example of how “might” could express something counterfactual.) Similarly I fail to see how “might” is more applicable to hypothetical situations than “may”.
e.g. “It might rain on Saturday.” and “It may rain on Saturday” convey the same message in relation to a hypothetical event.
As far as the “remotely possible” aspect is concerned, this is handled by voice tones rather than choosing between may and might..
e.g. “She /may/ want to come” = “She /might/ want to come. Here, by emphasizing ‘may’ or ‘might’ the possible is converted to remotely possible.
Looking now at your own example sentences, it is clear that “You may go home now, John.” is functionally identical with your example sentence for “Giving permission”, “Thank you. You may go now” and is not related to possibility as much as it is to permission. Similarly, your example sentence “I might be a few minutes late.” could easily be replaced by “I may be a few minutes late.” without any change of meaning. After using English for 70 years (many of them as a teacher), I can’t sense any significant difference.
In summary, there is nothing in the examples you give which explain any significant difference between “may” and “might” in relation to possibility which is relevant to learners of English. Furthermore, use of terms such as “counterfactual” and “hypothetical” are, in this context and without good examples showing any relevance they might have, confusing to English learners.
I have chosen the first usage “Possibility” to comment on. However, I must also say that some other distinctions between you make between the use of “may” and “might” are also debatable, with one exception. This is that when Giving Permission, it would certainly be wrong to say “Thank you. You might go now.” I would also suggest that while “Might I have the bill, please” is not as elegant as “May I have the bill, please?” it would not be noticed as an error at a table of native English speakers.