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[prin-suh-puh l] /ˈprɪn sə pəl/
an accepted or professed rule of action or conduct:
a person of good moral principles.
a fundamental, primary, or general law or truth from which others are derived:
the principles of modern physics.
a fundamental doctrine or tenet; a distinctive ruling opinion:
the principles of the Stoics.
principles, a personal or specific basis of conduct or management:
to adhere to one's principles; a kindergarten run on modern principles.
guiding sense of the requirements and obligations of right conduct:
a person of principle.
an adopted rule or method for application in action:
a working principle for general use.
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.
the method of formation, operation, or procedure exhibited in a given case:
a community organized on the patriarchal principle.
a determining characteristic of something; essential quality.
an originating or actuating agency or force:
growth is the principle of life.
an actuating agency in the mind or character, as an instinct, faculty, or natural tendency:
the principles of human behavior.
Chemistry. a constituent of a substance, especially one giving to it some distinctive quality or effect.
Obsolete. beginning or commencement.
in principle, in essence or substance; fundamentally:
to accept a plan in principle.
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.
1350-1400; Middle English, alteration of Middle French principe or Latin prīncipium, on the analogy of manciple. See principium
Can be confused
principal, principle (see usage note at principal; see synonym study at the current entry)
1, 2, 3. 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. 2. theorem, axiom, postulate, proposition. 5. integrity, probity, rectitude, honor.
Usage note Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for principles
  • He taught himself the principles of photography at the age of 14.
  • Those are the principles on which I do not intend to compromise.
  • Beyond that, the balancing principles of contrast and repetition come into play.
  • They each teach about scientific principles and important skills, and have direction for useful crafts and fun projects.
  • And we are confident in principles that unite and lead us onward.
  • While not theologically deep or biblically rigorous, it is full of wise principles, useful lists and practical leadership tips.
  • Personal stories illustrate that eight principles are central to forging the path to achievement.
  • From her I learned the basic principles of book design and layout, and the importance of exacting attention to detail.
  • For this reason, parents should explain the principles behind the new rules.
  • With out the principles the details just lean in a random, ever changing, direction.
British Dictionary definitions for principles


a standard or rule of personal conduct: a man of principle
(often pl) a set of such moral rules: he'd stoop to anything, he has no principles
adherence to such a moral code; morality: it's not the money but the principle of the thing, torn between principle and expediency
a fundamental or general truth or law: first principles
the essence of something: the male principle
a source or fundamental cause; origin: principle of life
a rule or law concerning a natural phenomenon or the behaviour of a system: the principle of the conservation of mass
an underlying or guiding theory or belief: the hereditary principle, socialist principles
(chem) a constituent of a substance that gives the substance its characteristics and behaviour: bitter principle
in principle, in theory or essence
on principle, because of or in demonstration of a principle
Usage note
Principle and principal are often confused: the principal (not principle) reason for his departure; the plan was approved in principle (not in principal)
Word Origin
C14: from Latin principium beginning, basic tenet


(Christian Science) another word for God
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for principles



late 14c., "origin, source, beginning; rule of conduct; axiom, basic assumption; elemental aspect of a craft or discipline," from Anglo-French principle, Old French principe "origin, cause, principle," from Latin principium (plural principia) "a beginning, commencement, origin, first part," in plural "foundation, elements," from princeps (see prince). Used absolutely for (good or moral) principle from 1650s.

It is often easier to fight for principles than to live up to them. [Adlai Stevenson, speech, New York City, Aug. 27, 1952]
Scientific sense of "general law of nature" is recorded from 1802. The English -l- apparently is by analogy of participle, etc.

Online Etymology Dictionary, © 2010 Douglas Harper
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principles in Medicine

principle prin·ci·ple (prĭn'sə-pəl)

  1. A basic truth, law, or assumption.

  2. A rule or law concerning the functioning of natural phenomena or mechanical processes.

  3. One of the elements composing a chemical compound, especially one that gives some special quality or effect.

  4. The essential ingredient in a drug.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Idioms and Phrases with principles


The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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