Hello

Be patient, deer, we have a long way to go.

'Can' is used:

·to express ability:
'My sister can succeed in college.'

·to expression permission:
'You can use the car this evening if you drive carefully.'

·to express theoretical possibility:
The surface of Mars can reach a temperature of 400 degrees in the daytime.'

- to make a request:
'Can you pass me the salt?'


'Could' is used:

·to express an ability in the past:
'I could win when I played tennis at college.'

·to express past or future permission:
'You could use the car this evening if you drive carefully.'
'You could have used the car yesterday if you had asked.'

·to express present possibility:
'I could pass my college examination.'

·to express possibility or ability in contingent circumstances:
'I could pass my college examination if I study hard.'

- to make a request:
'Could you pass me the salt?'

The same relationship holds between active (agent is the subject) and passive (agent is not the subject) as with 'will' . Here is the completed paradigm, deer:

'Can' is used:

·to express ability:
'My sister can succeed in college.'
'My sister can be driven to college by her classmate.'

·to express permission:
'You can use the car this evening if you drive carefully.'
'The car can be used this evening by anyone who needs it.'

·to express theoretical possibility:
'The surface of Mars can reach a temperature of 400 degrees in the daytime.'
'Mars can be reached by rocket.'

- to make a request:
'Can you pass me the salt?'
'Can my car be fixed by noon?'



'Could' is used:

·to express an ability in the past:
'I could win when I played tennis at college.'
'My sister could be driven to college, because her roommate had a car.'

·to express past or future permission:
'You could use the car this evening if you drive carefully.'
'You could have used the car yesterday if you had asked.'
'My car could have been used for travel before the accident.'
'My car could be used if you promise to drive safely.'

·to express present/future possibility:
'I could pass my college examination.'
'My car could be used by my grandchildren if it continues to run well.'

·to express possibility or ability in contingent circumstances:
'I could pass my college examination if I study hard.'
'The exams could be passed with hard study.'


- to make a request:
'Could you pass me the salt?'
'Could my car be fixed by noon?'

Hi Deer,

'May' and 'might' are related by psychological or social (but not temporal) distance; they are usually interchangeable. 'Might' is more remote than 'may', but neither normally has a 'past' meaning, except by using the 'have' + -ed form: 'I may/might have left my wallet at home.'

Again, the passive has the same relationship to the active as we saw with 'can/could': the object of the active verb becomes the subject of the passive verb.

-for possibility:

'The police may arrest me tomorrow.'
'The police might arrest me tomorrow.' (considered a slightly more remote possibility than with 'may')
'I may be arrested (by the police) tomorrow.'
'I might be arrested (by the police) tomorrow.'

-for permission:

'May I use the car tonight?'
'Might I use the car tonight?' (the speaker is slightly more remote in status, i.e. is more polite)
'May your garden be photographed (by our horticultural club)?'
'Might your garden be photographed (by our horticultural club)?'

-for wishes ('may' only, and an uncommon usage):

'May you have a Merry Christmas!'
'I hope your son may not be bullied at boarding school next year.'

Hi Deer,

Here are the basics:

Must. The active/passive relationship is the same as for the other modals.

- for certainty:

'We all must die and pay taxes.'
'I hear the church bells-- it must be Sunday.'
'Jim is listening to music-- his homework must be finished.'

- for necessity/obligation:

'I must stop drinking-- alcohol is a poison.'
'A dog must be walked twice a day.'
'I must visit my aunt this weekend-- I haven't seen her for a long time.'
'Income tax must be paid by April 15th.'