Must not, Mustn't We use
must not to say that something is not permitted or allowed, for example:
- Passengers must not talk to the driver.
Structure of Must notMust is an
auxiliary verb. It is followed by a
main verb. The structure for
must not is:
subject +
must not + main verb
The main verb is the base verb (infinitive without "to").
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Must not is often contracted to mustn't. |
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Look at these examples:
subjectauxiliary must + notmain verb
I | mustn'tforgetmy keys. |
You | mustn'tdisturbhim. |
Students | must notbelate. |
NB: like all auxiliary verbs,
must CANNOT be followed by "to". So, we say:
- You mustn't arrive late. (not You mustn't to arrive late.)
Use of Must notMust not expresses prohibition - something that is
not permitted, not allowed. The prohibition can be subjective (the speaker's opinion) or objective (a real law or rule). Look at these examples:
- I mustn't eat so much sugar. (subjective)
- You mustn't watch so much television. (subjective)
- Students must not leave bicycles here. (objective)
- Policemen must not drink on duty. (objective)
We can use
must not to talk about the
present or the
future:
- Visitors must not smoke. (present)
- I mustn't forget Taha's birthday. (future)
We cannot use
must not to talk about the
past. We use other structures to talk about the past, for example:
- We were not allowed to enter.
- I couldn't park outside the shop.