- 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.