prin·​ci·​ple | \ˈprin(t)-s(ə-)pəl, -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

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.

Principle vs. Principal

Yes, these two words are confusing; we see evidence of the misuse of both in newspapers and books which have been overseen by professional editors, so don’t feel bad if you have trouble with them. Principle only functions as a noun (such as “a comprehensive and fundamental law, doctrine, or assumption”); if you want it to be an adjective you must use the word principled. Principal, on the other hand, may function as a noun (such as the head of a school) or as an adjective (meaning “most important”). 

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

Companies including Microsoft, Facebook and Axon, a maker of police body cameras, have formed AI ethics boards and Google published a set of more-general AI principles in June. Dina Bass, The Seattle Times, "Privacy groups urge tech firms to sign Safe Face Pledge to restrict use of facial recognition," 12 Dec. 2018 That math underscores principles that William P. Lauder, executive chairman of the Estée Lauder Companies, says have been baked into the DNA of his family’s business since its inception. Mattie Kahn, Glamour, "How Many Women Does It Take to Change a Congress?," 10 Oct. 2018 Still the application of aerodynamic principles at the time was aimed at cutting drag. Jonathan M. Gitlin, Ars Technica, "How a day driving high-downforce cars at VIR taught me I’m OK being slow," 11 Sep. 2018 The principles are the same: dry powder, mix with water. Sophie Wirt, Allure, "Exclusive: Tatcha Is Giving Its Fan-Favorite Rice Enzyme Powder a Makeover," 31 July 2018 Many of the same principles apply, so let’s examine seven common themes. Mark Daly, idahostatesman, "Constructing your financial house takes as much care as building your dream home," 20 June 2018 Standing is a strange little procedural requirement that the Supreme Court pretends to wield impartially and according to a neutral set of principles. Cristian Farias, Daily Intelligencer, "Why the Supreme Court Keeps Dodging the Question of Partisan Gerrymandering," 18 June 2018 Read below for 12 of Bourdain’s dining-out principles that will likely alter yours as well. 1. Sophie Dodd,, "Don't Order Fish on Mondays, Plus 9 More Dining Out Tips We Learned from Anthony Bourdain," 11 June 2018 But this is where the organizing principle of a nation state doesn’t work because these are going to be global issues and require global solutions. Peter Kafka, Recode, "Twitter CEO Jack Dorsey talked to NYU’s Jay Rosen for an hour, on the record. Read and listen to the full interview here.," 14 Sep. 2018

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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Statistics for principle

Last Updated

16 Dec 2018

Look-up Popularity

Time Traveler for principle

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

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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 \

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 \

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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More from Merriam-Webster on principle

Rhyming Dictionary: Words that rhyme with principle

Spanish Central: Translation of principle

Nglish: Translation of principle for Spanish Speakers

Britannica English: Translation of principle for Arabic Speakers

Comments on principle

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