May, Might, and Could for Possibility
Expressing Uncertainty
When we’re not sure about something, we use may, might, or could.
May - Possibility (50%)
Present Possibility
- She may be at home. (perhaps she is)
- It may rain later. (perhaps it will)
- He may know the answer. (perhaps he does)
Future Possibility
- I may go to the party. (I haven’t decided)
- They may arrive late. (it’s possible)
- We may need more time. (possibly)
Might - Possibility (40%)
Slightly less certain than “may”:
Present Possibility
- She might be at home. (possibly, I’m not sure)
- It might rain later. (there’s a chance)
- He might know. (maybe, maybe not)
Future Possibility
- I might go to the party. (I probably won’t, but maybe)
- They might not come. (there’s a chance they won’t)
- Things might change. (it’s possible)
Could - Possibility (Alternative)
“Could” also expresses possibility, similar to “might”:
Theoretical Possibility
- She could be at home. (it’s a possibility)
- It could rain. (one possibility)
- He could be right. (maybe he is)
One of Several Options
- We could go to the cinema. (one option)
- You could try calling her. (suggestion)
- This could be the answer. (one possibility)
Comparison Table
| Modal | Certainty | Example |
|---|---|---|
| must | ~95% | He must be at work. |
| may | ~50% | He may be at work. |
| might | ~40% | He might be at work. |
| could | ~40% | He could be at work. |
| can’t | ~5% | He can’t be at work. |
Negative Forms
May not / Might not
- She may not come. (perhaps she won’t)
- He might not know. (perhaps he doesn’t)
Note: “Mayn’t” is very rare. “Mightn’t” is used in British English.
Couldn’t (impossibility, not possibility)
- He couldn’t be there. = He can’t be there. (impossible)
May/Might/Could Have - Past Possibility
modal + have + past participle
- She may have left already. (perhaps she left)
- They might have forgotten. (perhaps they forgot)
- He could have misunderstood. (perhaps he misunderstood)
When expressing present or future possibility, the modals may, might, and could are largely interchangeable. Might typically implies the lowest probability, while may is slightly more formal. All three are followed by the bare infinitive.