Student or Learner
1. We us affirmativ and question forms of 'must' ad ' have to' to express
EXAMPLE: you "must" start rom here. Do i " have to start from here?
2. We use 'mustn't' / must not " t express prohibation.
EXAMPLE: ou "mustn't " switch on the computer before quiting the program.
3. We use 'need not'/ needn't" and 'do/des not have to'' to say that there's no obligation to do something.
EXAMPLE: youneedn't/ don't have to send a message . Just phone them.
Note: There's no past form of must. We use "had to" and "did not / didn't ahve to '' to express obligation and absence of obligation in the past.
EXAMPLE: I missed the bus yesterday. So i "had to" walk to school.