prin·​ci·​ple | \ ˈprin(t)-s(ə-)pəl How to pronounce principle (audio) , -sə-bəl \

Definition of principle

1a : 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
2 : a primary source : origin
3a : an underlying faculty or endowment such principles of human nature as greed and curiosity
b : an ingredient (such as a chemical) that exhibits or imparts a characteristic quality
4 capitalized, Christian Science : a divine principle : god
in principle
: with respect to fundamentals prepared to accept the proposition in principle

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Principle vs. Principal: Usage Guide

Evidence of confusion between principle and principal can be found even in publications overseen by professional editors. To keep these words straight, remember that principle functions only as a noun, and in its most common uses refers to a basic rule or law, as in "a guiding principle" or "a matter of principle." If you are looking for an adjective form of this word, you must use principled, as in "taking a principled stand." Principal functions as both a noun and an adjective. The noun has various meanings referring to someone with controlling authority ("the school principal") or in a leading position ("the ballet’s two principals"), but also has meanings relating to finance, law, and architecture. As an adjective, principal typically means "most important," as in "the principal reason."

Examples of principle in a Sentence

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 His investment strategy is based on the principle that the stock market offers the best returns for long-term investors. the basic principles of hydraulics
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Recent Examples on the Web But the marketplace of ideas in a democracy is supposed to follow a different principle: one person, one vote. Vivek Ramaswamy, National Review, "Corporate America’s Siege on Democracy," 13 Apr. 2021 The first had to do with the principle of disinterestedness, which called for partisan politics to be kept out of scholarship and the classroom. Louis Menand, The New Yorker, "The Making of the New Left," 15 Mar. 2021 Now the ancient Hindu principle of ahimsa, an exhortation to do no harm and revere life, is being used to encourage Hindus in North America to embrace the vaccine, said Dr. Kashyap Patel, a cardiologist in Atlanta who is a medical adviser to BAPS. New York Times, "Clergy Preach Faith in the Covid Vaccine to Doubters," 14 Mar. 2021 Even the few soccer team owners who refuse gambling money, on principle, end up taking it just by competing. New York Times, "The Gambling Company That Had the Best Pandemic Ever," 26 Mar. 2021 Conservatives should oppose federal industrial policy on principle. Cameron Hilditch, National Review, "The Department of Education Is as Useful as a Screen Door on a Submarine," 24 Mar. 2021 When our Republican majority stood on principle and refused to wreck the rules, our Democratic colleagues happily used the filibuster themselves. Mitch Mcconnell, WSJ, "The Scorched-Earth Senate," 17 Mar. 2021 For Wikipedia to reject this steady stream of money, to throw up objections based on principle, would perhaps seem as quixotic and stubborn as those homeowners who turn down a big check from a real estate developer planning a new skyscraper. Noam Cohen, Wired, "Wikipedia Is Finally Asking Big Tech to Pay Up," 16 Mar. 2021 Casanega would later disagree with the Vietnam War, but the Japanese attack on Pearl Harbor inspired him to enlist on principle in the Navy and become a pilot, flying torpedo bombers. Eric Branch, San Francisco Chronicle, "The last living original 49er: Ken Casanega's remarkable life reaches 100," 13 Mar. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'principle.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of principle

14th century, in the meaning defined at sense 1a

History and Etymology for principle

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

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Time Traveler for principle

Time Traveler

The first known use of principle was in the 14th century

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Statistics for principle

Last Updated

18 Apr 2021

Cite this Entry

“Principle.” Dictionary, Merriam-Webster, Accessed 19 Apr. 2021.

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More Definitions for principle



English Language Learners Definition of principle

: 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


prin·​ci·​ple | \ ˈprin-sə-pəl How to pronounce principle (audio) \

Kids Definition of principle

1 : a general or basic truth on which other truths or theories can be based scientific principles
2 : a rule of conduct based on beliefs of what is right and wrong
3 : a law or fact of nature which makes possible the working of a machine or device the principle of magnetism


prin·​ci·​ple | \ ˈprin(t)-sə-pəl How to pronounce principle (audio) \

Medical Definition of principle

1 : a comprehensive and fundamental law, doctrine, or assumption
2 : an ingredient (as a chemical) that exhibits or imparts a characteristic quality the active principle of a drug

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