[Note: This post was updated on April 30, 2020.]
Q: When I taught 8th-grade grammar back in the ’70s, I used to tell my students that “may” meant permission, while “might” meant possibility. Is that no longer the case? I often hear the words used interchangeably now.
A: That’s not the case. There are two issues here. As a modal auxiliary verb (a subject we wrote about in 2012 and 2018), “may” can be used to indicate permission. But “may” is also used—like “might”—to indicate likelihood or possibility.
So when speaking about the possibility of something’s happening, you can use either “may” or “might.” You can say, “I might go,” or “I may go.” Let’s explain this possibility business by quoting a section from Pat’s grammar and usage book Woe Is I (4th ed., 2019):
May is a source of our word maybe, and that’s a good clue to how it’s used. We attach it to another verb (may take or may forget or may have learned, for example) to show that something is or was possible.
We can use might in the same way, attaching it to a main verb to indicate possibility (might take, might have forgotten, might learn). Then how do we know which to choose as our auxiliary, or “helping,” verb—may or might?
Tradition says that what may happen is more possible than what might happen. But never mind. Today most people see little or no difference in the degree of possibility, and that old distinction is largely ignored. In modern English, may and might are interchangeable—almost. Grammarians still recommend might in certain cases.
Here’s what to remember.
• If the sentence has only one main verb (with or without have), you can accompany it with either may or might. Here we’re talking about things that are still possible.
Hermione may [or might] take the train.
Hermione may [or might] have taken the train.
She may [or might] forget her wand.
She may [or might] have forgotten her wand.
She may [or might] learn new tricks at the conference.
She may [or might] have learned new tricks at the conference.
• If the sentence has an additional verb in the present tense (underlined here), you can use either may or might with the other verb. Here again, we’re talking about things that are still possible.
Hermione thinks she may [or might] take the train.
She is afraid she may [or might] have forgotten her wand.
She says she may [or might] learn new tricks at the conference.
• If the sentence has an additional verb in the past tense (underlined here), I recommend using might with the other verb, though may is often seen in informal English. Here we’re talking about things that were possible in the past.
Hermione thought she might take the train.
She was afraid she might leave [or might have left] her wand behind.
She said she might learn new tricks at the conference.
Why use might in speaking of possibilities from the past? Since might is technically the past tense of may, it mixes better with past-tense verbs.
NOTE: Because there’s an “iffy,” hypothetical element in may and might, they’re often used in if statements. Don’t let that throw you. Just follow the rules above about using either may or might when there are other present-tense verbs and might when there are other past-tense ones: If Hermione goes to the Arithmancy lecture tonight, she may [or might] run into Professor Vector. If Hermione went to the Arithmancy lecture tonight, she might run into Professor Vector. If Hermione had gone to the Arithmancy lecture tonight, she might have run into Professor Vector.
What Might Have Been
In some kinds of sentences, as you’ve just seen, there’s not much difference between might and may. Here comes one now: Moose might [or may] have flunked the course. Both versions express a possibility: Moose could have flunked.
But sometimes might branches out on its own. It no longer acts like a version of may, so it loses its sense of possibility and becomes negative. This might—often it’s a might have—is about things that are contrary to fact.
Here’s the kind of sentence I mean: Given enough time, Moose might have graduated. This means that in retrospect, he didn’t have enough time, so he didn’t graduate.
When we’re being contrary, we often use might and might have to speak of nonevents—things that “might be” but aren’t, or that “might have been” but weren’t. Here are some more examples of this contrary‑to‑fact might:
“You might have helped me move that heavy armoire,” snapped Moose’s mom. (He didn’t help.) “You might tell me next time you have to miss a test,” said Moose’s professor. (He didn’t tell the prof.) Had Moose gone to class, he might have learned something. (He didn’t learn.) If Moose hadn’t played hooky, he might not have flunked. (He did flunk.)
Only certain kinds of situations lend themselves to a contrary‑to‑fact might. This is the might that refers to possibilities that never came to pass, or that reproaches someone who fails to fulfill an expectation. (Sometimes, the failure is our own, so we reproach ourselves: “I might have known!”)
As for the issue of “can” versus “may” when asking for permission, we wrote a blog item about this in 2017.
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