MODAL VERBS

MODAL VERBS

1. Give additional information about the function of the main verb

   • FULL MODALS
     • MUST
       • Express personal obligation
     • SHOULD
       • In the present or future, they are used to
         • Ask or give chill advice
         • Express an opinion
         • Make a suggestion
         • Express mild obligation
       • More common, less informal
       • In the past
         • Shouldn't + have + past participle
           • To express regret about something that happened in the past
           • Express criticism about something somebody has done
         • Should + have + past participle
           • Express regret about something that didn't happened in the past
           • Express criticism of somebody's behaviour
     • FORBIDDENS
       • Negative form
         • MUSTN'T
           • Express that the action is prihibited, illegal or dangerous. Can be an order.
             • The obligation comes from the speaker, usually has authority.
         • CAN'T
           • Express witholding permission and tells us that something is against the rules
             • The speaker doesn't have any authority over you. Is more informal.
               • Musn't is stronger and more authoritative than can't.
     • HAD BETTER
       • Is used to
         • Give strong advice
         • Express threat or warning
         • Refers only to the present or future
         • If it's negative, is "had better not"
     • POSSIBLITY
       • COULD
         • 50% certain to happen (half)
         • In negative form [could not / couldn't] means that is impossible
         • With present perfect [+ have + past participle]
           • Express that something was possible in the past but didn't happen.
           • Express that you want to make a guess about something that happened in the past.
           • Express that you were able to do something, but you didn't want to do it.
       • MIGHT
         • 40 - 50% certain to happen (less)
         • May / might
           • In the negative form [+ not], express improbability
           • With present perfect [+ have + past participle], express posibility in the past
       • MAY
         • 60 - 70% certain to happen (strong)
       • In the present or future
     • DEDUCTIONS
       • In the present or future
         • Can't + base form, express a NEGATIVE deduction. We believe that something is possible.
         • Must + base form, express a POSSITIVE deduction. We are almost certain that something is true.
       • In the past
         • Must + have + past participle, express a POSSITIVE deduction. We are almost certain that something happened in the past.
         • Can't / couldn't + have + past participle, express a NEGATIVE deduction. We are almost certain that something didn't happen.
   • SEMI MODALS
     • HAVE TO
       • Express external obligation
     • Ought to
       • Less common, more formal
   • FULL OR SEMI MODAL
     • NEED TO
       • Express necessity.
         • It can be use in two negative forms
           • Don't or doesn't need to / didn't need to
             • The first meens the same than needn't at present or future, but the second one (in the past) means that somthing wasn't nessesary and neither was done.
           • Needn't
             • In the present or future espress lack of necessity or obligation. In the past means that something wasn't nessesary but was already done.