principle

(noun) a basic generalization that is accepted as true and that can be used as a basis for reasoning or conduct. Synonyms: rule. Example: "Their principles of composition characterized all their works."

(noun) a rule or standard especially of good behavior. Examples: "A man of principle." "He will not violate his principles."

(noun) a basic truth or law or assumption. Example: "The principles of democracy."

(noun) a rule or law concerning a natural phenomenon or the function of a complex system. Synonyms: rule. Examples: "The principle of the conservation of mass." "The principle of jet propulsion." "The right-hand rule for inductive fields."

(noun) rule of personal conduct. Synonyms: precept.

(noun) (law) an explanation of the fundamental reasons (especially an explanation of the working of some device in terms of laws of nature). Synonyms: rationale. Examples: "The rationale for capital punishment." "The principles of internal-combustion engines."