| Auxiliary
| Uses
| Present / future
| Past
|
| may
| 1. polite request
2. formal permission 3. less than 50% certainty
| May I borrow your pen? You may leave the room. A: Where's Tom? B: He may be at the office.
| He mayhavebeen at the office.
|
| might
| 1. less than 50% certainty 2. polite request
| A: Where's Tom? B: He might be at the office. Might I borrow your pen?
| He might have been at the office.
|
| should
| 1. advisability 2. 90% certainty
| I should help my father in the morning. She should pass the exam! (future only, not present)
| I should have helped my father yesterday. She should have passed the exam!
|
| ought to
| 1. advisability 2. 90% certainty
| I ought to study tonight. She ought to do well on the test. (future only, not present)
| I ought to have studied last night. She ought to have studied last night.
|
| had better
| 1. advisability with threat of bad result
| You had better be on time, or we will leave without you.
| (past form uncomon)
|
| be supposed to
| 1. expectation
| He is supposed to come at 12.
| He was supposed to come at 12.
|
| be to
| 1. strong expectation
| You are to be here at 9:00.
| You were to be here at 9:00.
|
| must
| 1. strong necessity 2. prohibition (negative) 3. 95% certainty
| 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.
|
| have to
| 1. necessity 2. 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 had to go to class yesterday.
|
| have got to
| 1. necessity
| I have got to go to class today.
| I had to go to class yesterday.
|
| will
| 1. 100% certainty 2. willingness 3. polite request
| He will be here at 6:00 ((future only). The phone's ringing. I'll get it.
Will you please pass the salt?
|
|
| be going to
| 1. 100% certainty 2. definite plan
| He is going to be here at 6:00 (future only) I'm going to paint my bedroom. (futureonly)
|
I was going to paint my room,
but I didn't have time.
|
| can
| 1. ability / possibility 2. Informal permission 3. Informal polite request 4. impossibility (negativeonly)
| I can run fast. You can use my car tomorrow. Can I borrow your pen? That can'tbe true!
| That can't have been true!
|
| could
| 1. past ability 2. polite request 3. suggestion 4. less than 50% certainty 5. impossibility (negative only).
| Could I borrow your pen? Could you help me? A: I need help in English. B: You could talk to your English teacher. A: Where's John? B: He could be at home. That couldn't be true!
| I could run fast when I was a child.
You could have talked to your teacher.
He could have been at home.
That couldn't have been true!
|
| be able to
| 1. ability
| I am able to help you. I will be able to help you.
| I was able to help him.
|
| would
| 1. polite request
2. preference 3. repeated action in the past
| Would you please ass salt? Would you mind if I left early? I would rather go to the park than stay home.
| I would rather have gone to the park. When I was a child, I would visit
my grandmother every weekend.
|
| used to
| 1. repeated action in the past
|
| When I was a child, I would visit my
grandmother every weekend.
|
| shall
| 1. polite question to make a suggestions 2. future with "I" or "we" as subject
| Shall I open the window? I shall leave at nine. (will =more common)
|
|
