|be supposed to||expectation||We are supposed to meet them here.||We were supposed to meet here.|
|be to||strong expectation||We are to meet them here.||We were to meet them here.|
|can / could
Can - Can't
informal polite request
|I can learn modal verbs online.
You can use my car tomorrow.
Can I borrow your book?
Cats can't swim.
| I could jump high a few years ago but now I can't.|
That can't have been true!
lack of necessity(negative)
|I have to go to class today.
I don't have to go to class today.
|I had to go to class yesterday.|
I didn't have to go to class yesterday.
|have got to||necessity||I have got to go to class today||I had to go to class yesterday.|
|had better||strongly advised||You had better be on time.||(past form uncommon)|
|may|| polite request
less than 50% certainty
| May I borrow your book?
You may leave the room.
He may be at the school.
He may have been at school.
|Might||less than 50% certainty||He might be at school.||He might have been at school.|
|I must go to class today.
You must not open that door.
Mary isn't in class. She must be sick.(present only)
| I had to go to class yesterday. |
Mary must have been sick yesterday.
|I ought to study tonight.|
She ought to be at school
| I ought to have studied last night. |
She ought to have done well on the test.
|shall||ask another person's opinion(only used with I or we)||Shall I invite them too?
Shall we dance?
|I should study tonight
He should be at school
| You should have paid your bills. |
He should have done well on the test.
|Legal obligation/official||MUST||Police officer: 'You must wear a seatbelt.'|
|Logical Conclusion||MUST||The teacher's absent. She must be sick.|
|Reporting a rule||BE SUPPOSED TO||We are supposed turn our cell phones off in movie theaters.|
|Personal necessity / obligation||HAVE TO / HAVE GOT TO||I have to call the doctor today.|
|Possibility||CAN||I can meet with you on Friday.|
|Ability||CAN / BE ABLE TO||I can play the piano. |
I am able to speak English.
|Permission||CAN / BE ALLOWED TO||I can have a dog in my apartment. I am allowed to have pets in my room.|
|Past Ability||COULD / WAS ABLE TO||When I was a kid, I could run for hours.|
could vs was were able to
|Past Permission||WAS ALLOWED / PERMITTED TO||I wasn't allowed to go out at nights.|
|Advice||SHOULD||You should call your mother on her birthday.|
|Warning||HAD BETTER||You'd better study before the test.|
|A Choice/Not required||DON'T HAVE TO||I don't have to wear a suit to work.|
|Possibility/uncertainty about the future|
|MAY / MIGHT||It might / may rain this evening.|
May be it will rain this evening.
|Polite request||WOULD / COULD||Would you open the door, please?|
|Permission||MAY / CAN / COULD||May I borrow your pen?|
|To express what you want||WOULD LIKE||I would like to learn English free.|
|Preference||WOULD RATHER||I would rather walking than driving.|