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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

He caveated his support as being for the principle of assisted dying and insisted he would want a requirement before any new law was implemented that hospices would be "properly funded and sorted out".

From BBC ● Jul. 29, 2026

“Death via organ donation” directly contradicts this principle, which is why it remains a concept that exists solely in the realm of academic exploration.

From The Wall Street Journal ● Jul. 28, 2026

The bills differ in detail but converge on one principle: data centers pay their own costs.

From MarketWatch ● Jul. 27, 2026

But when it comes to how he'll apply what he thinks in principle to what he does in practice, that was not always so clear.

From BBC ● Jul. 27, 2026

Heisenberg's uncertainty principle shows that there is no possible way to measure the pencil’s length—or an electron’s position—and its velocity with perfect accuracy at the same time.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

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

“They have to have fundraisers to get a car fixed. Jamie Principle never made a dollar from any of his records.”

From BBC ● Oct. 16, 2024

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

“All of these companies have a hard time to find blue-collar labor,” said Zhou Linlin, the chief executive of Principle Capital, a Shanghai investment firm with stakes in numerous Chinese factories.

From New York Times ● Dec. 8, 2023

In 1798, writing under a pseudonym, Malthus had published an incendiary paper—An Essay on the Principle of Population—in which he had argued that the human population was in constant struggle with its limited resource pool.

From "The Gene" by Siddhartha Mukherjee

Tehran said earlier this week that it had held talks with Oman, which also borders the strait, on "common principles and operational mechanisms" to ensure the safe passage of shipping.

From Barron's ● Jul. 29, 2026

Meta is committed to building with the principles of individual empowerment, invention and balance of power.

From The Wall Street Journal ● Jul. 28, 2026

While the Apple Upgrade option only requires a soft credit pull, consumers should approach this choice with the same principles they would in evaluating whether any leased asset fits in with their financial lives.

From MarketWatch ● Jul. 28, 2026

Translated into constitutional terms, Minnesota argued that the surge violated federalist principles by invading the state’s reserved police powers: the broad authority to govern public health, safety, welfare, and order.

From Slate ● Jul. 27, 2026

Aristotelian philosophy had been based on the idea that one ought to be able to deduce sciences from generally accepted first principles, so that all science would be comparable to geometry.

From "The Invention of Science" by David Wootton

Related Words

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