Modal verbs II
Obligation, prohibition, advice and lack of obligation
Modal verbs expressing obligation are: must and have to; advice: should and ought; prohibition: mustn't and lack of obligation: don't have to and needn't
| VERB | MODAL VALUE |
USE |
EXAMPLES |
| must |
*1obligation, present and future |
+ | I really must stop smoking You must be here by 8 o'clock at the latest |
| have to | *2obligation, present, past and future |
+ ? | She has to work today Did she have to work yesterday? |
| *3should | advice or recommendation in present and future |
+ - ? | John should get a haircut. He shouldn't smoke. |
| mustn't | prohibition, present and future |
- |
You mustn't smoke in the classroom. |
| don't have to | lack of obligation, present, past and future |
- | You don't have to eat that. She won't have to take another course. |
| need/needn't | lack of obligation, present and future |
- ? | Need we go shopping tomorrow? We needn't go shopping tomorrow |
- = used in negative sentences
? = used in questions
*1 When we use 'must' this usually means that some personal circumstance makes the obligation necessary (and the speaker almost certainly agrees with the obligation.)
I must go to bed earlier.*2 When we use 'have to' this usually means that some external circumstance makes the obligation necessary. Remember that "have to" is not even a modal verb.
They must do something about it.
I have to arrive at work at 9 sharp. My boss is very strict.
We have to give him our answer today or lose out on the contract.
*3 "ought to" has the same uses as "should": advice and recommendation. The only difference between both modals is the use of "TO" before the infinitive.
Exercise
You should use the elevator if you do not want to get exhausted.
A high tower must be used in any city with tall buildings.
If you are interested in getting the most of this tower, you should buy the Total Tower Experience ticket.
If you must be careful with your expenses...
...you should buy the Observation Experience.
You should not walk on this place if you are afraid of heights!
You must not smoke inside the building.
1- What do they express?
| OBLIGATION | ADVICE |
PROHIBITION |
LACK OF OBLIGATION |
|
|
2- Do you know a synonym for 'should'?
1. When you are in Britain you drive on the left.
2. In Spain, you overtake on the right.
3. You drive at more than 120 km/h.
4. If you are ill, you go to the doctor.
5. He's shortsighted so he wear glasses when he drives.
6. If you have such a bad cough, you smoke so much.
7. There's too much traffic, you go by train.
Further practice
1. You be here before 8.30. It's not necessary to arrive so early.
2. You study harder if you want to get a university degree.
3. You wear a uniform if you go to an English Secondary School.
4. You
drink alcohol if you are under 18.
5. You book the hotel in advance in case there are no rooms left.
6. Mark study French. It's optional.
7. Marta do that. It's forbidden.
Practice on the Internet
Learn more about 'must' and 'should' and practice a bit by clicking on this website. Then have some further practice on these modal verbs by clicking here.
Practice 'must', 'have to', 'should' and 'ought to' by clicking here.
Do this exercise on the difference between 'must' and 'have to'.
Here are some good exercises on 'mustn't' and 'don't have to'.
Finally practice must, have to and should on this website.