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 Letting people register themselves online is a good idea in principle but how well it can be implemented is a big concern, said Becky Lewallen, Washington County Clerk. Doug Thompson, Arkansas Online, "Online registration proposed for voters," 27 Feb. 2021 Perry once again spoke up for the Texas principle of independence from federal oversight, ignoring how much its vaunted independence had just cost in lives and destruction. Michael Hiltzik, Los Angeles Times, "Column: The Texas crisis reminds us that ‘natural’ disasters are almost always manmade," 22 Feb. 2021 Unelected heads of government are in principle a snub to democracy. The Economist, "From banker to prime minister Mario Draghi gives Italy another chance," 20 Feb. 2021 But the paper itself, at least in principle, seems sound. Quanta Magazine, "In Violation of Einstein, Black Holes Might Have ‘Hair’," 11 Feb. 2021 But like every other gene-manipulation method, CRISPR works better in principle than in practice. John Horgan, Scientific American, "Premature Freak-Outs about Techno-Enhancement," 23 Jan. 2021 The New York Jets have reached an agreement in principle with San Francisco 49ers defensive coordinator Robert Saleh to become their new head coach. Steve Gardner, USA TODAY, "New York Jets set to hire Niners' Robert Saleh as head coach," 15 Jan. 2021 State health officials agreed with the idea in principle — because age is one of the strongest risk factors for severe COVID-19 and deaths — but worried about expanding access to a level that far exceeds the available supply of doses. Jeremy Olson, Star Tribune, "Minnesota's COVID vaccine supply reaches 558K," 13 Jan. 2021 Trump is doing this for the principle, not just for power. Isaac Chotiner, The New Yorker, "Why Representative Mike Johnson Thinks That the Election Isn’t Over," 15 Dec. 2020

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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Learn More about principle

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

1 Mar 2021

Cite this Entry

“Principle.” Dictionary, Merriam-Webster, Accessed 5 Mar. 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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