วันพฤหัสบดีที่ 12 มกราคม พ.ศ. 2555

บทที่ 14 - เกี่ยวกับการใช้กิริยากับกิริยาช่วย (MODALS)

    CAN and COULD
    MAY and MIGHT
    WILL and WOULD
    SHOULD
    MUST
    HAD BETTER
    HAVE TO
Modals, also referred to as modal verbs or modal auxiliaries, are words such as: can, could, may, might, will, would, should, must, had better. These are helping verbs, each of which has more than one meaning that we placed before the main verbs to express: ability, possibility, necessity, certainty, make polite requests, or ask for permission, and more.
1. CAN and COULD
Can and could are modal verbs. They are used with other verbs to convey ideas such as possibility, permission, etc.
We use can:
v  to talk about possibility and ability;
EXAMPLE: I can ride a horse.
EXAMPLE: He can speak three languages.
v  to make requests or give orders;
EXAMPLE: Can you buy me a can of beer?
EXAMPLE: Can you complete now what you are doing?
v  to ask for or give permission.
EXAMPLE: Can I come in now?
Note: we may also use could, may and might for permission.
    when we decide we are able to do something for the present or future.
EXAMPLE: We can have our dinner now.
EXAMPLE: We can go swimming tomorrow.
Could is one of the modal verbs. We use could:
v  as the past tense of can.
EXAMPLE: Jane said she could get the tickets for us.
v  when we wish to be very polite.
EXAMPLE: Could I go now, please?
v  to show what was possible in the past.
EXAMPLE: He could cycle when he was four years old.
v  to ask someone to do something.
EXAMPLE: Could you buy some cigarettes for me?
v  to show the ability to do something.
EXAMPLE: My grandmother could speak Spanish.
v  to show that one is allowed to do something.
EXAMPLE: We could choose to do the course we wanted.
v  for an action now or in the future.
EXAMPLE: It's a nice day. We could go for a walk.
EXAMPLE: When I go to London next week, I could stay with my uncle
v  for something that should have been done in the past.
EXAMPLE: I was so tired. I could have slept the whole day.
v  with present perfect tense for things which were possible to happen but didn't or an event which we are not sure about.
EXAMPLE: You could have taken a different route to avoid the traffic jam.
EXAMPLE: He could have broken the glass. / She couldn't have broken the glass.
Points to note:
v  We do not use can with infinitive verb.
EXAMPLE: We can play football today. (NOT: We can to play football today.)
v  We commonly use Can I to offer to do something
EXAMPLE: Can I help you to do it
v  Sometimes it is necessary to use (be) able to in place of can.
EXAMPLE: I can't contact him. / I haven't been able to contact him for two days. (It is not possible to use can with present perfect tense).
v  Where the subject is singular, we do not add –s to the verb following can or could
EXAMPLE: He can swim. (NOT: He can swims.)
EXAMPLE: We could smell burning. (NOT: We could smells burning)
v  Could is less sure than can, so we use could when we do not really mean what we say.
EXAMPLE: I am so hungry. I could eat the whole chicken. (NOT: I can eat the whole chicken).
2. MAY and MIGHT
We use may or might to:
*      make a suggestion or an assumption.
EXAMPLE: Everyone is looking for George. He may/might be in the toilet.
*      indicate that something is a possibility.
EXAMPLE: What we are told may/might be true.
*      possibly take the place of could.
EXAMPLE: That man over there looks like Mike. He could/may/might be Mike.
*      say about something that is possible to happen in the future.

EXAMPLE: We may visit them in Birmingham for the summer holidays.
EXAMPLE: They might go out later when the weather improves.
(For these two examples, we can also use might visit or may go.)
*      For something that happened in the past, we can use may have or might have.
EXAMPLE: She may have been asleep when the burglar entered the house.
EXAMPLE: The police think he might have seen the robbery and are looking for him.
*      We use ‘might’, and not ‘may’, for an unreal situation.
EXAMPLE: If I met her again, I might ask for her telephone number.
(It is quite unlikely that I meet her again, so I don’t get to ask for her telephone number. We do not use may here.)
*      We can use the continuing form with may/might.
EXAMPLE: I may/might be reading in the library this evening.
*      We can use be going with may/might.
EXAMPLE: We may/might be going to Australia next month. // We may/might go to Australia next month. (These sentences do not change in meaning)
3. WILL and WOULD
Ø  We use will and would for polite questions.
EXAMPLE: Will/would you phone me later?
Ø  for invitations
EXAMPLE: Will/would join us for a drink?
Ø  for offering something
EXAMPLE: Would/wouldn't you like a coffee or tea?
Ø  for asking someone to do something
EXAMPLE: Will/would you please top grumbling about the weather?
4. SHOULD
We use should
Ø  for a strong suggestion.
EXAMPLE: You should go back to him. (It's not a 'must' but it would be good to do so.)
Ø  for advice and recommendations.
EXAMPLE: You should not be going now. It's going to rain anytime.
Ø  for something that is right or morally right to do.
EXAMPLE: You should cut down on your heavy drinking.
Ø  when something is not right or normal.
EXAMPLE: They should be queuing up
Ø  for something or something fair to happen.
EXAMPLE: She has been shoplifting, so she should be caught.
Ø  for the present moment.
EXAMPLE: You look tired. You should go to bed now.
Ø  in place of ought to. (No difference in meaning here.)
EXAMPLE: I think you should/ought to make more time for yourself to relax.
Ø  with if.
EXAMPLE: If Jane should come while I'm out, please tell her to wait.
5. MUST
o   We use must when we feel something is true.
EXAMPLE: You have been talking for so long your mouth must be very dry now.
o   We use must when it is necessary to do something.
EXAMPLE: I haven't seen my parents for a long while. I must visit them at the weekend.

o   We can use must for the present or future.
EXAMPLE: We must leave now before the weather gets worse.
EXAMPLE: We must leave very early tomorrow or we will be late.
o   We use must have for something that we think happened in the past.
EXAMPLE: He must have gone out while I was sleeping.
6. HAD BETTER
    We usually use had better to give advice or warning or make a suggestion about something bad that is likely to happen.
EXAMPLE: You are coughing loudly. You had better see a doctor.
EXAMPLE: I am overeating. I had better go on a diet.
EXAMPLE: We think she had better not befriend him. He is a drug addict.
ü  Had better can be replaced by should/ought to and retain the meaning.
EXAMPLE: You are coughing loudly. You should/ought to see a doctor.
EXAMPLE: I am overeating. I should/ought to go on a diet.
EXAMPLE: We think she should/ought to befriend him. He is a drug addict.
7. HAVE TO
We use have to:
v  to show it is necessary to do something.
EXAMPLE: I have to leave now as they are waiting for me.
v  when circumstances dictate that we do something.
EXAMPLE: He has to see the doctor every month to treat his skin disorder.
v  for the present or future.
EXAMPLE: All of us have to attend a meeting now.
EXAMPLE: We have to work late tomorrow.
v  with the past tense.
EXAMPLE: We had to do the training in order to be eligible.
v  in place of have got to. There is no difference in meaning.
EXAMPLE: I have to/have got to give a talk tomorrow.