Study materials
Here are two sentences with the same word. The job it does in them is completely different.
It may rain later.
May I use your phone?
First a guess, then a request for permission. Might and could behave the same way. So the topic splits in two: possibility first, politeness second.
A guess: all three mean "maybe"
Some good news to start with. In the sense of possibility may, might and could are interchangeable, and there is no need to agonise over the choice.
He may be stuck in traffic.
She might be busy.
We could miss the train.
There is a shade of difference: might sounds slightly more cautious than may. But it is a shade, not a rule, and none of the three would count as a mistake.
The form is the same for all of them and very simple. The base verb follows, with no to. The modal word itself never changes, so there is no such thing as mays or mights.
Requests and permission: the steps of politeness
The second half of the topic is asking. Here the three words are no longer equal: they line up from the everyday to the formal.
| Form | Tone | Example |
|---|---|---|
| Can I | casual, among people you know | Can I sit here? |
| Could I | polite, fits almost anywhere | Could I sit here? |
| May I | formal and fairly official | May I sit here? |
When you are asking not for permission but for a favour from another person, could you takes over.
Could you repeat that, please?
Could you help me with this box?
Such requests are usually answered without any modal at all: Yes, of course, or Sure, go ahead.
Could has one more job
Keep this one separate: could is also the past of can in the sense of being able to.
I could swim when I was five.
She couldn't find the address.
This causes no confusion: the meaning is visible from the sentence. Past ability comes with a specific time; a guess comes without one.
The negative: maybe it will not happen
May not and might not are not a ban but the opposite guess: perhaps this will not happen.
He might not come.
It may not work.
One warning. In official texts and on signs, may not does mean a prohibition: Visitors may not enter. In everyday speech a ban is mustn't or can't, which you met in the previous topic.
The mistakes everyone makes
The first is calling in do for a question or a negative.
Does he might come? → Might he come?
The second is adding an s in the third person.
She mays call later. → She may call later.
The third is putting to after the modal.
It might to rain. → It might rain.
All three are caught by one habit. A modal word is already a helper in itself, so it needs neither do, nor s, nor to.
Try it right now
Think about tomorrow and say two guesses about it in English with may or might.
Then imagine asking two different people for a favour: a close friend and a stranger in an office. Say both requests and listen to the step of politeness change.