CAN:
Ability = They can play basket very well.
Possibility = They can pass their final exams easily
Inability / Impossibility = I’m sorry. We can’t fix it.
Asking for permission (informal) = Can I go out tonight, dad?
Requests (informal) = Can you help me, Mary?
Deduction (negative) = He can´t be English. He´s speaking French.
COULD:
Ability in the past = He gave up his old job so he could work for us.
Speculation = He could be Spanish or South American.
Asking for permission (formal) = Could I ask a question?
Requests (formal) = Mr Smith, could you say it again more slowly?
Suggestions = We could eat at a restaurant together.
Future possibility = I think we could have another war.
MUST:
Moral obligation : I must study hard to pass my final exams.
Deduction (affirmative) : He must be from Spain. He´s speaking Spanish.
Prohibition (negative) = We mustn’t take photographs in the museum.
BE ALLOWED TO
Permission = Students are not allowed to use their mobile phones at school
HAVE TO :
External obligation = I have to work from 9 to 5 every day.
Absence of obligation (negative) = We don´t have to get up early on Sundays.
MAY:
Speculation = He may be Spanish or South American.
Asking for permission (formal) = May I have another cup of coffee, sir?
Future possibility = China may become a major economic power.
OUGHT TO / SHOULD:
Advice = We ought to/should find a solution to this problem.
NEEDN¨T :
Absence of obligation = We needn´t get up early on Sundays.
MIGHT:
Future possibility = They might give us a 10% discount.
Speculation = He might Spanish or South American.
SHALL:
Offers = Shall I help you with your homework?
Suggestions = Shall we meet at 2.30?
Asking what to do = Shall I stay or not?
WILL:
Predictions = Profits Will increase next year.
Instant decisions = The phone’s ringing! I´ll anwer it.
Promises = I’ll get back to you first thing on Monday.
WOULD:
Stating or asking preferences (formal) = Would you prefer tea or coffee?
Asking for permission (formal) = Would you mind if open the window?
Making a request (formal) = Would you pass the salt please?
Invitation (formal) = Would you like to have lunch with met?
Making arrangements (formal) = Would 3 o´clock suit you?
