Modal verbs of deduction – summary chart
We use may and might to talk about things that are possibly true, but we don’t know for sure.
- He’s more than 2 meters tall. He might be a basketball player. (=perhaps he is)
- He says Betty is his friend, but I think she may be his girlfriend.
We use may not or might not to talk about things that are possibly not true, but we don’t know for sure.
- You should call her. She might not know where you are. (=perhaps she doesn’t know)
We don’t use can as a modal of deduction.
- He might/may be at home now. (NOT
He can be at home now)
We use must when we are sure, or quite sure, that something is true.
- You must be tired after the long journey. (=I’m sure you are tired)
- I’m sure I had the keys when I left. They must be in the car.
But we use can’t (NOT
mustn’t) when we are sure, or quite sure, that something is not true.
- We’ve been walking for hours. It can’t be far from here. (NOT
It mustn’t be far)
- They’ve lived here only for a couple of months. They can’t know many people.
+ be -ing
After may, might, must or can’t we can use be + -ing, when we are talking about actions in progress.
- They’ve gone to Ibiza, and right now they must be having a great time.
- Call him. He might be waiting for us.