Modal verbs
You must do it !
He had to go there!
He ought to help her!
They can run very fast!
I could run very fast when I was young!
I won’t be able to go to the theatre tomorrow!
Need I wash up? -No, you needn’t!
Can Ability, possibility, probability, doubt, surprise Could Ability, possibility in the past; offers, request May Probability, asking and giving permission Must Obligation, prohibition, necessity Have to Necessity, moral duty Be to Plans and arrangements Ought to Moral duty Need Necessity (in questions and negative sentences) Should Advice, moral duty, obligation