English

Contraction

mustn't

1. must not; used to indicate that something is forbidden or, in a tag question, that something is not necessary.

   If you see a hedgehog, you mustn't touch it.

   You mustn't blame yourself.

   We must go, mustn't we?

   • 1906, Edith Nesbit, The Railway Children, Chapter 4: The engine-burglar,

     "Now, listen," said Mother; "it's quite true that we're poor, but we have enough to live on. You mustn't go telling everyone about our affairs--it's not right. And you must never, never, never ask strangers to give you things. Now always remember that--won't you?"

   • 1989: Batman (movie)

     Look, we mustn't mistake ourselves for regular people. We're artists.

Related terms

• shouldn't
• can't
• oughtn't

See also

• Appendix:English modal verbs
• Appendix:English tag questions