Understanding “Must” and “Mustn’t” in English Grammar

“Must” and “mustn’t” are important modal verbs used to express obligation and prohibition. They help us understand rules, responsibilities, and restrictions. This article will explain how to use “must” and “mustn’t” correctly, along with examples and exercises for practice.

When to Use “Must”

“Must” is used to express:

• Obligation (something that is necessary to do)
• Rules and laws
• Strong advice

Examples:

• I must go home now; it’s late. (Obligation)
• You must wear a life jacket when sailing. (Rule)
• He is sick; he must take his medicine regularly. (Strong advice)

When to Use “Mustn’t”

“Mustn’t” (must not) is used to express:

• Prohibition (something you are not allowed to do)
• Warnings about danger

Examples:

• You mustn’t make noise in the library. (Rule)
• You mustn’t play with fire. (Warning)
• Passengers mustn’t speak to the driver while the bus is moving. (Safety rule)

Practice Exercises

1. Choose the correct answer (“must” or “mustn’t”)

1. You ________ be home on time.
2. You ________ use your mobile phone here; it’s not allowed.
3. We ________ respect our teachers.
4. You ________ cheat during the tests.
5. You ________ ride a bike without a helmet.
6. You ________ take permission if you want to go to the toilet.
7. You ________ throw your litter on the ground.
8. You ________ brush your teeth every day.
9. We ________ run around the swimming pool; it’s dangerous!
10. You ________ wash your hands before eating.

Sentence Building Exercise

Use the words (play – smoke – brush – wash) to create sentences with “must” and “mustn’t”:

Why Learning “Must” and “Mustn’t” is Important

• Helps understand rules and laws
• Improves clarity in speaking and writing
• Enhances communication skills
• Essential for school, work, and daily life

Conclusion

Understanding “must” and “mustn’t” helps learners follow rules, express obligations, and avoid mistakes. By practicing with examples and exercises, you can master these modal verbs and use them correctly in everyday situations.

Must – Mustn’t

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