mustn't

mustn't

You mustn't touch the hot stove.

Definition
  1. Contraction (modal verb):
    • Prohibition: "mustn't" is the contraction of "must not," used to express a strong prohibition or requirement that something is not allowed or should not be done. It indicates an obligation to avoid a particular action.
Usage Examples
  • (It is strictly forbidden to touch the hot stove.)
  • (Students are prohibited from running in the hallways.)
  • (It is required that we do not forget to lock the door.)
Advanced Usage

  • "mustn't" vs. "don't have to": "mustn't" expresses a prohibition, while "don't have to" indicates a lack of necessity.

    • You mustn't smoke here. (Smoking is forbidden.)
    • You don't have to smoke here. (Smoking is not required, but it is allowed.)

  • "mustn't" in polite requests: Occasionally used in formal or polite speech to emphasize a prohibition.

    • You mustn't worry about the details; I will handle them. (It is important that you do not worry.)
Variants and Related Words

  • Must not (full form): the uncontracted version of "mustn't."

    • You must not enter this area without permission. (The full form of the prohibition.)

  • Must (modal verb): the positive form, expressing necessity or obligation.

    • You must wear a seatbelt. (It is required to wear a seatbelt.)
Synonyms
  • Cannot: used to express a prohibition or impossibility.
    • You cannot enter without a ticket. (Entry is not allowed.)
  • Shall not: a formal or legal expression of prohibition.
    • The tenant shall not sublet the property. (Subletting is prohibited.)
  • Is not permitted to: a formal way to express a prohibition.
    • He is not permitted to leave the building. (Leaving is forbidden.)
Related Idioms

  • Mustn't grumble: a British informal expression meaning one should not complain or express dissatisfaction.

    • The weather is a bit cold, but I mustn't grumble — it's better than rain. (I should not complain about the weather.)

  • If you must: used to reluctantly allow something that is not fully approved.

    • If you must eat that chocolate, at least share it. (If you are determined to eat it, do so under conditions.)