IV. Grammar Review: Modal verbs of advice, obligation, possibility and necessity
We can use “should” and “shouldn’t” to give or ask for advice:
- You should stop smoking before it’s too late.
For strong advice we can use “must” or “mustn’t”:
- You mustn’t give up yet, try just once more.
We often use “must” when obligation comes from the person speaking or writing:
- We must buy a gift for our visitor.
We use “mustn’t” to say that something is prohibited or not allowed:
- You mustn’t use a mobile phone on board a plane.
We often use “have to” to show that the obligation comes from another person or institution, not the speaker:
- While driving you have to fasten yourself with a fasten belt.
We use “don’t have to” in situations where it is not necessary to do something:
- Friday is a public holiday and we don’t have to work.
We use “may” when there is only a possibility that something will or will not happen:
- The situation may improve in the longer term.
A. Choose the most appropriate modal verb. There are situations where both verbs are possible. Can you say why?
1. Foreign visitors must / should carry an identity card at all times when being abroad.
2. Passengers mustn’t / don’t have to smoke anywhere on the aircraft.
3. You don’t have to / mustn’t enter the radioactive zone in Chernobyl.
4. I think you should / must learn how negotiate in Japan. It would be a very useful skill if you had the time to learn it.
5. You don’t have to / shouldn’t travel so much – you are looking very ill.
6. All personnel of the company should / must wear the uniform while in the building.
7. When doing business abroad one should / must get to know about the business etiquette of the host country.
8. Tomorrow is a religious holiday, so you mustn’t / don’t have to work.
9. Next Friday is possible. I must / may be available early in the morning.
10. We may be in for a rough crossing, there is a storm coming.