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• principle
  principle

  noun

  an accepted or professed rule of action or conduct.
• Principle
  Principle

  noun

  Christian Science another word for God

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principle

American  

[prin-suh-puhl] / ˈprɪn sə pəl /

noun

• principles
  plural

1. an accepted or professed rule of action or conduct.

   a person of good moral principles.

2. a fundamental, primary, or general law or truth from which others are derived.

   the principles of modern physics.

   Synonyms:

   proposition, postulate, axiom, theorem

3. a fundamental doctrine or tenet; a distinctive ruling opinion.

   the principles of the Stoics.

4. principles, a personal or specific basis of conduct or management.

   to adhere to one's principles; a kindergarten run on modern principles.

5. guiding sense of the requirements and obligations of right conduct.

   a person of principle.

   Synonyms:

   honor, rectitude, probity, integrity

6. an adopted rule or method for application in action.

   a working principle for general use.

7. a rule or law exemplified in natural phenomena, the construction or operation of a machine, the working of a system, or the like.

   the principle of capillary attraction.

8. the method of formation, operation, or procedure exhibited in a given case.

   a community organized on the patriarchal principle.

9. a determining characteristic of something; essential quality.

10. an originating or actuating agency or force.

    growth is the principle of life.

11. an actuating agency in the mind or character, as an instinct, faculty, or natural tendency.

    the principles of human behavior.

12. Chemistry. a constituent of a substance, especially one giving to it some distinctive quality or effect.

13. Obsolete. beginning or commencement.

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idioms

1. in principle, in essence or substance; fundamentally.

   to accept a plan in principle.

2. on principle,

   1. according to personal rules for right conduct; as a matter of moral principle.

      He refused on principle to agree to the terms of the treaty.

   2. according to a fixed rule, method, or practice.

      He drank hot milk every night on principle.

principle ¹ British  

/ ˈprɪnsɪpəl /

noun

1. a standard or rule of personal conduct

   a man of principle

2. (often plural) a set of such moral rules

   he'd stoop to anything

   he has no principles

3. adherence to such a moral code; morality

   it's not the money but the principle of the thing

   torn between principle and expediency

4. a fundamental or general truth or law

   first principles

5. the essence of something

   the male principle

6. a source or fundamental cause; origin

   principle of life

7. a rule or law concerning a natural phenomenon or the behaviour of a system

   the principle of the conservation of mass

8. an underlying or guiding theory or belief

   the hereditary principle

   socialist principles

9. chem a constituent of a substance that gives the substance its characteristics and behaviour

   bitter principle

10. in theory or essence

11. because of or in demonstration of a principle

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Principle ² British  

/ ˈprɪnsɪpəl /

noun

1. Christian Science another word for God

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principle More Idioms  

1. see in principle; on principle.

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Usage

Principle and principal are often confused: the principal (not principle ) reason for his departure; the plan was approved in principle (not in principal )

Commonly Confused

See principal.

Synonym Usage

Principle, canon, rule imply something established as a standard or test, for measuring, regulating, or guiding conduct or practice. A principle is a general and fundamental truth that may be used in deciding conduct or choice: to adhere to principle. Canon, originally referring to an edict of the Church (a meaning that it still retains), is used of any principle, law, or critical standard that is officially approved, particularly in aesthetics and scholarship: canons of literary criticism. A rule, usually something adopted or enacted, is often the specific application of a principle: the golden rule.

Other Word Forms

Noun Inflected Forms

• principles
  plural

Etymology

Origin of principle

First recorded in 1350–1400; Middle English, alteration of Middle French principe or Latin prīncipium, on the analogy of manciple; see principium

Explanation

A principle is a kind of rule, belief, or idea that guides you. You can also say a good, ethical person has a lot of principles. In general, a principle is some kind of basic truth that helps you with your life. "Be fair" is a principle that guides (or should guide) most people and businesses. A politician who tries to do the right thing rather than win votes is acting on principle. A person who has principles is a good, decent person. On the other hand, if you say someone has no principles, that means they're dishonest, corrupt, or evil.

Example Sentences

See Examples For:

principle Principle principles

In principle, that could mean traveling continuously in one direction would eventually return you to where you started, much as traveling around Earth can bring you back to your starting point.

From Science Daily ● Sep. 28, 2026

“Current law says that the guiding principle for the management of the forests is maximum sustained production of high-quality wood products,” he told The Times.

From Los Angeles Times ● Sep. 23, 2026

Direct compensation removes the focus of an undergraduate education as the core principle of collegiate athletics.

From The Wall Street Journal ● Sep. 22, 2026

The same principle applies to some of the more disturbing scenarios.

From MarketWatch ● Sep. 22, 2026

The principle at issue was straightforward: natural facts must be replicable and reproducible if they are to count as facts at all.

From "The Invention of Science" by David Wootton

Ehrlich was often labeled a neo-Malthusian, a reference to the 18th-century British political economist Thomas Malthus, best known for “An Essay on the Principle of Population.”

From The Wall Street Journal ● Mar. 17, 2026

Principle "cannot be set aside", he said, but he vowed to take a "pragmatic" approach, emphasising both the economic and military importance of the UK-US relationship.

From BBC ● Jan. 19, 2026

The Premack Principle is a motivational behavioral technique based on a reward system.

From Los Angeles Times ● Jan. 20, 2025

Thus a key Principle of our rule of law is that we must "respect, support, and defend the constitutional rights of all Americans" with fairness and due process of law.

From Salon ● Sep. 3, 2024

Maddie has a rule about passing on favors, which she calls the Aerodrome Drop-Off Principle.

From "Code Name Verity" by Elizabeth Wein

Beneath the rotunda, Trump also showed Xi the US constitution, the document that set out the principles of the country's democratic government two and a half centuries ago.

From Barron's ● Sep. 25, 2026

Similar principles could help researchers think about how artificial intelligence systems might handle conflicting streams of information and decide which signals to trust.

From Science Daily ● Sep. 24, 2026

Three decades on, the cutting edge of chess technology is artificial intelligence programmed to rediscover the wide world of possibilities from first principles.

From The Wall Street Journal ● Sep. 23, 2026

He told them he wants a "single set of global principles and standards that are very much about unlocking the full potential whilst guarding against the risks".

From BBC ● Sep. 22, 2026

And Thomas Jefferson’s lyrical rendering of the reasons for the entire revolutionary enterprise emphasized the self-evident character of the principles at stake.

From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis

Related Words

• assumption
• basis
• convention
• doctrine
• ethic
• foundation
• fundamental
• precept
• proposition
• regulation
• rule
• truth