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

In principle, Mike Yurk of Hudson agrees with that fishing strategy. Paul A. Smith, Milwaukee Journal Sentinel, "Smith: Retro outing proves fishing fun - and gear - is timeless," 14 July 2018 Related Greece and Spain were the only countries that agreed in principle to take migrants back, a move important for Ms. Merkel to avert a political crisis that brought her government close to collapse. Nektaria Stamouli, WSJ, "Germany Delays Greece’s Final Bailout Payment," 12 July 2018 After the civil war, population and voting were, in principle if not in Jim Crow practice, aligned. The Economist, "America’s electoral system gives the Republicans advantages over Democrats," 12 July 2018 Motel 6 has agreed in principle to settle the lawsuit, the deal is subject to the approval of a federal judge. Jacques Billeaud, azcentral, "Motel 6 to settle claim workers gave guest info to ICE," 9 July 2018 Motel 6 has agreed in principle to settle the lawsuit. Jacques Billeaud, The Seattle Times, "Deal struck to settle discrimination suit against Motel 6," 9 July 2018 The Bulls agreed in principle to trade point guard Jerian Grant to the Magic in a three-team deal that will bring the Bulls shooting guard Julyan Stone from the Hornets once the trade is finalized, a source said. K.c. Johnson,, "Bulls to trade Jerian Grant, get guard Julyan Stone in three-team trade," 7 July 2018 The Charlotte Hornets have a deal in principle to sign Frenchman Tony Parker as their veteran backup to point guard Kemba Walker, an NBA source confirmed to the Observer. Rick Bonnell, charlotteobserver, "Source: Charlotte Hornets to sign former San Antonio Spur Tony Parker," 6 July 2018 Activists feel emboldened by a recent agreement in principle in New York City to subsidize fares for as many as 800,000 residents who live below the poverty line. Adam Vaccaro,, "Groups want the T to provide fare discounts for low-income riders," 6 July 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

21 Oct 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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Comments on principle

What made you want to look up principle? Please tell us where you read or heard it (including the quote, if possible).


exaggeratedly or childishly emotional

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