Formal & Official:
* Rule: A specific directive or principle that must be followed.
* Law: A formal body of rules enforced by the state.
* Standard: A benchmark or measure of quality or performance.
* Ordinance: A local law or decree.
* Statute: A written law enacted by a legislature.
* Code: A systematic collection of laws or regulations.
* Policy: A course of action adopted by an organization or government.
Informal & General:
* Control: The power to influence or direct.
* Guideline: A general principle or suggestion.
* Restriction: A limitation or constraint.
* Directive: An instruction or order.
* Prescription: A specific requirement or condition.
The best word to use depends on the specific context. For example, if you're talking about a formal rule enforced by a government, "regulation" or "law" would be appropriate. If you're talking about a general principle or suggestion, "guideline" or "directive" might be better choices.