mustn't

Definition

must not (negative auxiliary); used to indicate that something is forbidden or, in a tag question, that something is not necessary.

Etymology

must + -n't

Example Sentences

• "You mustn't blame yourself for this tragedy."
• "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?""