• I may not be coming in tomorrow...
  • I might not be coming in tomorrow...

When should I use "may" and when should I use "might"?


13 Answers 13


Formally, might is the past tense of may. In situations where the past tense is required, only might may be used:


He said he might go.

Subordinate clauses in English must be in the past tense if the main clause is in the past tense, so this is correct.


He said he may go.

Here you cannot use the present tense may with the past tense main verb said.

However, in the present tense may and might can be used interchangeably, meaning that all of the following are correct:

He says he may go.
He says he might go.
He may go.
He might go.

  • "Subordinate clauses in English must be in the past tense if the main clause is in the past tense, so this is correct."
    – Dan
    Commented Apr 25, 2011 at 15:16
  • "Subordinate clauses in English must be in the past tense if the main clause is in the past tense, so this is correct." That isn't an accurate description of English, JS. "I will go to Tokyo" --> She said she will go to Tokyo OR, She said she would go to Tokyo, which is certainly a viable possible as an optional backshift. But these backshifts that occur for reported speech have nothing at all, that's zero to do with tense. They ONLY serve to mark the speech as reported. "She" hasn't gone to Tokyo yet so how could/can it have anything to do with tense/time?
    – Dan
    Commented Apr 25, 2011 at 15:23
  • 1
    @Dan: I think there's a subtle point you are missing here. If the mysterious "she" says "I will go to Tokyo", she is indicating that her voyage to Tokyo is in the future, i.e. it is at a time later than now. Saying "She said she would go to Tokyo" is indicating that the voyage was in the future, i.e. it is at a time later than the (past) time when she was speaking. That is what it has to do with tense. I grant that reported speech muddies the waters, but "As it turned out, she would go there later that year" is perfectly grammatical without any reporting going on.
    – psmears
    Commented Apr 25, 2011 at 18:01
  • @Dan: That said, I agree that it is possible to use "will" with past reported speech - adding a little more context makes it sound more natural: "I asked her just now, and she said she will go when the weather improves" (versus "She said she would go when the weather improved, and she did").
    – psmears
    Commented Apr 25, 2011 at 18:03
  • @Dan How could 'She said she will…' work, there? Commented Apr 17 at 17:46

Might is also the past subjunctive of may. Because of this, in some cases these aren't interchangeable; if you're using the subjunctive to form a feeling of conditionality, may is rather inappropriate. For example, "If you were the King, then you might be able to do that."

In the same way, you can use might to form more polite questions: "Might I join you?" as opposed to "May I join you?"

  • 10
    I'm not sure if "Might I join you" is actually perceived as more polite than "May I join you?".
    – Marthaª
    Commented Nov 2, 2010 at 21:59
  • Martha, I know you didn't make that up because I've seen sources say that before, and at some point somewhere in the world that might have been the case, but I can tell you that today in most of the English-speaking world it's the opposite. 'Might' is far more common than 'may' making it less formal. If a boy asks a girl out and uses 'might' it almost always comes off sounding very casual. "May I ask you out?" is the most formal sounding. 'May' connotes permission = formality. 'Might' connotes possibility (not permission) = less committed / friends = more casual. That's my opinion anyway.
    – Brillig
    Commented Aug 21, 2014 at 3:28
  • Most people today would not say “May I join you?” or “Might I join you?” Today, most if not all people will say “Can I join you?” “Can,” which signifies ableness, has replaced “may” which connotes permission; we use “can” to ask for permission as opposed to “may.” “May” (and by extension “might”) is considered a formal and polite way of asking someone for something.
    – user305707
    Commented Jul 15, 2018 at 1:24


We can use 'may' to ask for permission. However this is rather formal and not used very often in modern spoken English. We use 'may' to suggest something is possible


We use 'might' to suggest a small possibility of something. Often we read that 'might' suggests a smaller possibility that 'may', there is in fact little difference and 'might is more usual than 'may' in spoken English.


  • I can certainly see asking for permission with "might I have one of those?" (Although "may" would be more common.) Commented Jul 30, 2012 at 0:42

In the present tense, they are interchangeable, though there is a subtle difference implied in the likelihood of the thing happening (you coming in tomorrow, in this case):

Most of the time “might” and “may” are almost interchangeable, with “might” suggesting a somewhat lower probability. You’re more likely to get wet if the forecaster says it may rain than if she says it might rain; but substituting one for the other is unlikely to get you into trouble—so long as you stay in the present tense. (source)


When could I use May and might?

Ia. Some people follow the rule that may can be considered a greater possibility than might.

“They both indicate that something is possible, but something that may happen is more likely than something that might happen.” Quick and Dirty Tips

“’May’ simply states the possibility or likelihood, while ‘might’ emphasizes the conditional nature of the possibility, introducing a greater level of uncertainty.” After Deadline NYT

Ib. However, in practice most people use may and might interchangeably in most cases.

“Often we read that might suggests a smaller possibility that may, there is in fact little difference and might is more usual than may in spoken English.” English Grammar secrets

IIa. May can be considered permission

Example: “Mother may I visit my friend?
"You may.”

II b. It is recommended to prefer might not over may not for clarity because may can be considered "permission"

According to Garner’s Modern American Usage (a bible for all grammar nuts like me), you should never use “may” in a negative hypothetical because the reader could read it to mean the person “does not have permission.” For example, saying “I may not go to the store” could be misread as “I am not allowed to go to the store.” In this case, you always use “might”: I might not go to the store.
Writer's Digest

III. It is recommended to prefer might have over may have for a hypothetical that didn’t happen

Example: when using “may have” and “might have” you can use either if the truth of a situation is still unknown (i.e. "I think your comment may have / might have offended some people"), but if the truth of the situation is known and you are speaking about a hypothetical alternative that did not occur, it’s clearer and more common to use “might have” (i.e. "If Brazil’s best player hadn’t been hurt, they might have won the World Cup").

IVa. Historically different tenses:

In historical practice for the usage of these words some people used “may” exclusively for present tense and “might” exclusively for past tense Oxford Dictionaries

IVb. Modal usage most commmon today

Today the words may and might are used as modals like would, should and could, meaning that they are generally used without regard to their historical tense and the modal used should reflect a slightly different meaning.

IVc. Even today, especially for some situations involving past tense, many people feel might is still not always interchangeable with may in normal usage.

For instance, because it sounds awkward to mix past tense and present tense, many people including myself would probably prefer “after I read that book, I knew I might visit London one day” to using 'may' (but if someone did use 'may' I could live with it, just wouldn't prefer it).

On the other hand, I find “Last night the weatherman said it may rain today” acceptable, especially because whether it will rain is something that is still an unknown.


Strictly speaking, "might" is the simple past tense of "may".

In practice, they're often used interchangeably in other tenses, as your example demonstrates.

  • See comment above.
    – Alan Hogue
    Commented Aug 5, 2010 at 22:58
  • Which comment? :-)
    – avpaderno
    Commented Jan 26, 2011 at 12:43

As it is with all the modal pairings, 'might' is not the past tense of 'may', nor is 'may' the present tense of 'might'. All modal verbs in modern English are tenseless. As tenseless verbs, modals are able to operate in any time sense, past, present or future.

As to their epistemic [level of certainty meanings] and their deontic [social meanings] they are never interchangeable. They, like all modals, have their nuances and those nuances are expressed by choosing one or the other.


As reported from the NOAD (New Oxford American Dictionary):

Traditionalists insist that one should distinguish between may (present tense) and might (past tense) in expressing possibility: I may have some dessert after dinner if I'm still hungry; I might have known that the highway would be closed because of the storm. In casual use, though, may and might are generally interchangeable: they might take a vacation next month; he may have called earlier, but the answering machine was broken.


In cases where the two might ;-) mean more or less the same thing wrt there being a chance that something will or can occur, it can make sense to use might instead of may when there is a possibility of confusion with another meaning of may.

E.g., "John may come" can mean either that it is possible that John will come or that John is allowed to come. "John might come", on the other hand, can only mean the former.

When you need to be clear about the sense, and the intended sense is possibility, using "might" can prevent ambiguity. In general, "may" is a slipperier critter.


I'll remember 3 things regarding may/might.

  1. Some people say Might is more conditional, i.e. has less certainty than May.
  2. Some people say Might is the same as May.
  3. Might can be used where May cannot: I thought I might die.

From the 17th edition of the Chicago Manual of Style:

May denotes either permission {you may go to the store} or possibility {I may go to the movies}...May most commonly connotes an uncertain possibility {you may find that assignment too difficult}, and it often becomes might {you might find that assignment too difficult}. Is there a connotative difference? Yes: may tends to express likelihood {we may get there on time}, while might expresses a stronger sense of doubt {we might get there on time—if the traffic clears}. Might can also express a contrary-to-fact hypothetical {we might have been able to make it if the traffic had been better}.”


May and might are historically different modal verbs which have drifted together in meaning in most types of English. This is a very common and normal process in all languages. May is still sometimes still used to ask permission, though that use is probably declining and you rarely hear it in American English.


All the above answers are correct, but there is another perspective to it. "May" and "Might", both are used to denote probability. "May" is used when the event is more likely to take place. "Might" is used when the overall probability of the event is less.


  • John is not severely sick and he is planning to go to office. We can use "may" in this case. - "John may come."
  • John is severely sick and he is planning to go office. We can use "might" in this case. -"John might come to office."

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