principle

noun prin·ci·ple \ˈprin(t)-s(ə-)pəl, -sə-bəl\

: a moral rule or belief that helps you know what is right and wrong and that influences your actions

: a basic truth or theory : an idea that forms the basis of something

: a law or fact of nature that explains how something works or why something happens

Full Definition of PRINCIPLE

a : a comprehensive and fundamental law, doctrine, or assumption

b (1) : a rule or code of conduct (2) : habitual devotion to right principles <a man of principle>

c : the laws or facts of nature underlying the working of an artificial device

: a primary source : origin

a : an underlying faculty or endowment <such principles of human nature as greed and curiosity>

b : an ingredient (as a chemical) that exhibits or imparts a characteristic quality

capitalized Christian Science : a divine principle : god

— in principle

: with respect to fundamentals <prepared to accept the proposition in principle>

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Usage Discussion of PRINCIPLE

Although nearly every handbook and many dictionaries warn against confusing principle and principal, many people still do. Principle is only a noun; principal is both adjective and noun. If you are unsure which noun you want, read the definitions in this dictionary.

Examples of PRINCIPLE

Urban guerrilla warfare was futile against a thermonuclear superstate that would stop at nothing to defend the profit principle. —Philip Roth, American Pastoral, 1997
Better, of course, to take a higher road, operate on the principle of service and see if things don't turn out better … —Richard Ford, Independence Day, 1995
Pointlessness was life's principle, and it spread its sadness. —Arthur Miller, Timebends, 1987
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Origin of PRINCIPLE

Middle English, from Middle French principe, principle, from Old French, from Latin principium beginning, from princip-, princeps initiator — more at prince

First Known Use: 14th century