A2 · Lesson 27 · 20 min
Rules, necessity and advice
In this lesson
- I can talk about rules and things that are necessary.
- I can say what is prohibited, optional or good advice.
Grammar in context
Maya has started a weekend job at a small cinema. On her first day, the manager explains the staff rules. Maya must wear her name badge, but she does not have to work every Saturday. Her friend Leo says she should arrive early and ask questions when she is unsure.
Which phrase means a rule, which means something is optional, and which gives friendly advice?
Have to and must for necessity
Use have to when a rule or situation makes something necessary. Use must for a strong rule or instruction. Both are followed by the base verb. In everyday speech, have to is very common. For questions, use do or does with have to: Do I have to bring ID?
- Staff have to wear black shoes.
- You must show your ticket at the door.
Mustn't and don't have to are different
Mustn't means that something is prohibited: do not do it. Don't have to means that something is not necessary, but you can do it if you want. Use don't or doesn't before have to. Do not use mustn't when you mean that an action is optional.
- Visitors mustn't take photos in the gallery.
- You don't have to stay until the end.
Should for advice
Use should to give advice or say what you think is a good idea. It is not a rule. Use should + base verb. For negative advice, use shouldn't + base verb. In questions, put should before the subject: Should I call her now?
- You should save the manager's phone number.
- He shouldn't drive when he is very tired.
Common mistakes
Compare the incorrect and corrected forms.
Avoid
When bringing lunch is optional: You mustn’t bring your own lunch.
Use
When bringing lunch is optional: You don’t have to bring your own lunch.
Mustn't prohibits an action; don't have to says it is optional.
Avoid
She shoulds wear a helmet.
Use
She should wear a helmet.
Should is followed by the base form, without -s.
Put it into practice
Try the exercises, write your own examples and check your understanding.