Verbi modali o servili difettivi = mancano di alcune forme (infinitive, past participle, gerund) Followed by dare infinitive Same form for all persons ( no –s) Use substitution forms fo infinitive and missing tenses e.g. can => to be able to must => to have to may => to be allowed to
obligation/ order Students must be at school on time intructions You must open the tin on this side strong recommendation You must this this film: it’s amazing deduction/speculation Where are my glasses? – They myst be in your bag
Should If you don’t feel well, you should stay at home, you shouldn’t go to school Ought to If she has asked for you help, you ought to help her, you oughtn’t to disappoint her. Had better We had better hurry if we don’t want to miss the bus What a cold! You’d better take an aspirin!
Necessity/external authority/duty She has to write an essay for tomorrrow We have to keep our homes neat and tidy We all have to be at school on time I can’t make it today: I’ve got lots of things to do!
Must (rule: speaker’s authority) Mum: “You must tidy up your room” The law: ”Cyclists must wear a helmet” to have to (duty/necessity/external autority) Son: “I have to tidy up my room” Cyclist :”I have to wear a helmet” (external authority) Cyclist “ I must wear a helmet” ( I feel it is important)
MUSTN’T prohibition You mustn’t smoke at school You can’t smoke… Don’t smoke… We weren’t allowed to ge into the gallery We couldn’t get into the gallery DON’T/DOESN’T HAVE TO absence of necessity We don’t have to wear a uniform She doesn’t have to wash up: she has a dishwasher We didn’t have to wait: the train earrived on time