n.
1.a basic generalization that is accepted as true and that can be used as a basis for reasoning or conduct
2.a rule or standard especially of good behavior
3.a basic truth or law or assumption
4.a rule or law concerning a natural phenomenon or the function of a complex system
5.rule of personal conduct
6.(law) an explanation of the fundamental reasons (especially an explanation of the working of some device in terms of laws of nature)