Yes, rule is a Scrabble word!

Verb

1. Exercise authority over; as of nations

2. Decide with authority

3. Be larger in number, quantity, power, status or importance

4. Decide on and make a declaration about

5. Have an affinity with; of signs of the zodiac

6. Mark or draw with a ruler

7. Keep in check

Noun

1. A principle or condition that customarily governs behavior

2. Something regarded as a normative example

3. Prescribed guide for conduct or action

4. (linguistics) a rule describing (or prescribing) a linguistic practice

5. A basic generalization that is accepted as true and that can be used as a basis for reasoning or conduct

6. The duration of a monarch's or government's power

7. Dominance or power through legal authority

8. Directions that define the way a game or sport is to be conducted

9. Any one of a systematic body of regulations defining the way of life of members of a religious order

10. A rule or law concerning a natural phenomenon or the function of a complex system

11. (mathematics) a standard procedure for solving a class of mathematical problems

12. Measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths