"Must Not" is a phrase used to indicate something that is prohibited or not allowed. It emphasizes the importance of avoiding a specific action or behavior. For example, in rules or guidelines, saying "You must not enter" clearly communicates that entry is forbidden. This phrase is often found in legal documents, safety instructions, and school policies. It serves to protect individuals and maintain order by outlining unacceptable actions. For instance, traffic laws may state, "You must not drive over the speed limit," highlighting the consequences of ignoring such rules.