principle

noun

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