Law

1. The body of rules and standards issued by a government, or to be applied by courts and similar authorities. You must obey the law.
2. A particular such rule. A new law forbids driving while on the phone.
3. A written or understood rule that concerns behaviors and the appropriate consequences thereof. "Do unto others as you wish them to do to you" is a good law to follow.
4. A well-establish, observed physical characteristic or behavior of nature. Newton's third law of motion states that for every action there is an equal and opposite reaction.
5. A police officer. Where is the law when you need one?