Luke ought not to drive so fast.
advice
I must go to the supermarket today to get Tim’s present.
obligation
May I close the window, please?
permission
You don’t have to wear your school uniform tomorrow.
no obligation
Fred won’t be able to get here until Sunday
ability
We mustn’t wear jewellery in school.
prohibition
You can finish this essay after class.
permission
Laura had to go to the bank yesterday.
obligation (past)
Mary should have gone alone.
advice
They didn’t have to do their homework until Friday.
no obligation (past)
Diane can play the piano very well
ability
The skiing trip will be a success, I’m sure.
certainty
The car should be fixed by now.
likelihood
I may start a new course next year.
possibility
Sara was not to drive the car without her father
prohibition
Amy could have spoken fluent German (if she had stayed in Bonn for longer).
possibility
Would you buy me a newspaper while you’re out, please?
requests