modals part two

Skill: Grammar  

Category: General English & Academic English

Level: Upper-Intermediate


Part Two

Using “Not have to” for lack of necessity and “must not” for prohibition: 

Lack of necessity:

When we use must and have to in negative form, they convey a different meaning.

Negative form: do not have = not necessary

Ex: We don’t have to go to the office tomorrow because it is holiday.

Ex: I can find you a job. You don’t have to worry about it.


When must not is used in negative form, it shows prohibition.

Negative form: must not = prohibition (do not do this)

Ex: You must not come to class late. (Coming late to class is forbidden or prohibited. In any condition you need to come on time)

Note. Must not is very strong, so the speakers usually use imperatives to express prohibition.

Ex: Don’t plagiarize your writing assignment anymore.

Ex: You’d better not to plagiarize your writing assignment.

Exercise. Complete the sentences with must not or do/does not have to

1. a) You have already finished your assignment so you ______________________ study today.

b) You ____________________ neglect doing your homework. Excuses are not accepted and will affect your performance and grade.

c) I ____________________ call my classmate. I found the information I was searching for.

2. I _____________ visit the doctor. I am not feeling better.

3. Students _______________ leave the class without the teacher’s permission.

4. A person ______________ get married to have a happy life.

Using “be supposed to” to express expectation

  • Be supposed to is used when someone expects something to happen as it was scheduled before.

Ex: The class is supposed to begin at 9 o’clock in the morning.

Ex: You were supposed to send me the letter by now.

  • Be supposed to is used to express when someone expects or requests a certain behavior.

Ex: I am supposed to finish my homework before I go to bed.

Ex: The children are supposed to respect the elders.

  • Use should to express expectations.

Ex: You should call me when you arrived home.  

Ex: The letter should be here soon.

Exercise. Answer the questions using be supposed to

  1. If you are stuck in traffic, what are you supposed to do?
  2. When you are in a hurry to go home and suddenly you see a person had an accident and needs your help, what are you supposed to do?

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