rule

noun:an official instruction or principle that states how things must be done or what is allowed
- The first rule of the club is to be respectful to all members.
verb:to exercise ultimate power or authority over an area and its people
- The king would rule the land for over fifty years.
noun:a standard method or procedure for solving a mathematical problem
- We learned the rule for calculating the area of a triangle.
verb:to dominate or be superior in a competition or situation
- The home team ruled the championship game from start to finish.
noun:a customary or habitual practice that is widely accepted
- It’s a rule around here to greet everyone with a smile.