Modal Verbs of Deduction

1. MODALS OF DEDUCTION

2. TO MAKE GUESSES ABOUT THE PRESENT
● must
● can’t
● may + infinitive
● might
● could

3. MUST
● We use it to express that something is
certain or highly probable.
If A is bigger than B, and B is bigger than C…
… then A must be bigger than C.
Mary keeps crying – she must have a
problem.

4. CAN’T, COULDN’T
● We use can’t to express that something is
not true or nearly impossible.
It can’t be the postman at the door. It’s only
seven o’clock.
● We use couldn’t to express that
something is impossible.
She couldn’t be working. She is on maternity
leave!

5. MAY, MIGHT, COULD
● We use them when there is a possibility of
it happening.
He could be working (Perhaps a 70% chance)
I may go to Edinburgh tomorrow (Perhaps a
50% chance)
Peter might come with me (Perhaps a 30%
chance. It is possible but not very likely to
happen)