noun

1. 1. an authoritative regulation for action, conduct, method, procedure, arrangement, etc. the rules of the school
   2. an established practice that serves as a guide to usage the rules of grammar
2. a complete set or code of regulations in a religious order the Benedictine rule
3. a fixed principle that determines conduct; habit; custom to make it a rule never to hurry
4. something that usually or normally happens or obtains; customary course of events famine is the rule following war
5. 1. government; reign; control
   2. the period of reigning of a particular ruler or government
6. a ruler or straightedge
7. Obsolete way of acting; behavior
8. Law
   1. a regulation or guide established by a court governing court practice and procedure
   2. a declaration, order, etc. made by a judge or court in deciding a specific question or point of law
   3. a legal principle or maxim
9. Math. a method or procedure prescribed for computing or solving a problem
10. Printing
    1. a thin strip of metal, the height of type, used to print straight or decorative lines, borders, etc.
    2. a line so printed

Etymology: ME reule < OFr rieule < L regula, ruler, straightedge < regere, to lead straight, rule: see right

transitive verb ruled, ruling rul′·ing

1. to have an influence over; guide to be ruled by one's friends
2. to lessen; restrain reason ruled his fear
3. to have authority over; govern; direct to rule a country
4. to be the most important element of; dominate action rules the plot
5. to settle by decree; determine the court ruled the validity of the point
6. 1. to mark lines on with or as with a ruler
   2. to mark (a line) thus

intransitive verb

1. to have supreme authority; govern
2. to be at a specified rate or level; prevail: said of prices, commodities, etc.
3. to issue a formal decree about a question