Mustn’t

We use “mustn’t” to express something:

• is not allowed.
• is prohibited.
• is important not to do.

We use it to express negative obligation.

The prohibition can be subjective or objective.

Examples of rules

You mustn’t smoke inside.

You mustn’t drink and drive.

Examples of subjective obligations

You mustn’t go to bed late.

You mustn’t tell anyone!

It’s your turn!

What are things we mustn’t do in the following places:

• An office.

  You mustn’t waste your time pranking your co-workers.

  

• A museum.

  You mustn’t touch anything that is on exhibition.

• A library.

  You mustn’t speak loudly or yell.