Permission, obligation and necessity

1. PERMISSION, OBLIGATION AND NECESSITY

2. THROUGH MODAL VERBS CAN, MUST Ex. : We can’t / mustn’t smoke in class SHOULD, OUGHT TO ( not so strong ) Ex. : We should / ought to do the English homework . We should / ought to have read more English books . ( when we regret something we didn’t do in the past ) HAD BETTER/HAD BETTER NOT ( stronger , a warning for the immediate future ) Ex. : You’d better not be late for the wedding .

3. THROUGH HAVE TO/ HAVE GOT TO HAVE TO : in all cases Ex. : Students have to do an exam at the end of the year . HAVE GOT TO : more colloquial , for specific occassions ( not general obligations ) Ex. : I’ve got to study for tomorrow’s exam . NOT HAVE TO: lack of necessity ( not obligation ). Ex. : We don’t have to wear a uniform at school .

4. NECESSITY NEED TO/DON’T NEED TO : in all cases. Ex. : I don’t need to wear glasses . NEEDN’T+INFINITIVE WITHOUT TO: on specific occasions . Ex. : You needn’t bring anything to the party . NEEDN’T HAVE+PAST PARTICIPLE/DIDN’T NEED TO+INFINITIVE: You did it but it wasn’t necessary . Ex. : I needn’t have bought /I didn’t need to buy any wine . I had three bottles in the cupboard ! DIDN’T NEED TO+INFINIVE: You didn’t do it because it wasn’t necessary . Ex. : We had lots of drinks and food at home so we didn’t need to g o to the supermarket for the party .

5. PERMISSION/OBLIGATION:OTHER EXPRESSIONS BE ABLE TO/BE ALLOWED TO: especially with a form or tense CAN doesn’t have . Ex. : I won’t be able to come to class tomorrow . You are not allowed to smoke in the building . BE PERMITTED TO: more formal, especially in announcements , signs for rules, regulations : Ex. : It’s not permitted to enter after the play has started . ( to be allowed to can’t be used after “ it ”) BE SUPPOSED TO: When the rules are not normally obeyed : Ex. : Students are supposed to turn off their mobiles in class , but most of them don’t .