Question

Look at the following pair of sentences. Underline the modals and discuss why each one is used in that sentence.

e.g. I must not take those pills. (I’m not allowed)  I need not take those pills. (It is not compulsory but I may if I wish.)

1. a) I can’t go to the meeting because I’m not a member. 
   b) I needn’t go to the meeting if I don’t wish to.
2. a) I can swim a length of the pool.
   b) I can swim in the pool on Saturdays.
3. a) You ought to get a nice present for her.
   b) You have to get a nice present for her.
4. a) Can I go to the toilet?
   b) May I be excused?
5. a) I may come tomorrow if I have the time.
   b) I might come tomorrow but it’s going to be difficult.

Answer 1

1. a) Can’t is used to show lack of permission.
   b) Needn’t is used to show that it is not necessary or compulsory.
2. a) Can is used to show ability.
   b) Can is used to show permission.
3. a) Ought to is used to show what is right or advisable.
   b) Have to is used to show necessity or obligation.
4. a) Can is used to ask for permission in an informal way.
   b) May is used to ask for permission in a more formal and polite way.
5. a) May is used to show possibility.
   b) Might is used to show a weaker or less certain possibility.