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From Middle English principle, from Old French principe, from Latin prīncipium (beginning, foundation), from prīnceps (first). By surface analysis, prīmus (first) +‎ -ceps (catcher); the former ultimately from Proto-Indo-European *preh₂- (before); see also prince.


  • IPA(key): /ˈpɹɪnsɪpəl/, /ˈpɹɪnsəpəl/
  • Audio (US):(file)
  • Hyphenation: prin‧ci‧ple
  • Homophone: principal



principle (plural principles)

  1. A fundamental assumption or guiding belief.
    Synonym: premise
    We need some sort of principles to reason from.
    • 2011 July 20, Edwin Mares, “Propositional Functions”, in The Stanford Encyclopedia of Philosophy, retrieved 2012-07-15:
      Let us consider ‘my dog is asleep on the floor’ again. Frege thinks that this sentence can be analyzed in various different ways. Instead of treating it as expressing the application of __ is asleep on the floor to my dog, we can think of it as expressing the application of the concept
           my dog is asleep on __
      to the object
           the floor
      (see Frege 1919). Frege recognizes what is now a commonplace in the logical analysis of natural language. We can attribute more than one logical form to a single sentence. Let us call this the principle of multiple analyses. Frege does not claim that the principle always holds, but as we shall see, modern type theory does claim this.
  2. A rule used to choose among solutions to a problem.
    The principle of least privilege holds that a process should only receive the permissions it needs.
  3. (sometimes pluralized) Moral rule or aspect.
    Synonym: tenet
    I don't doubt your principles.
    You are clearly a person of principle.
    It's the principle of the thing; I won't do business with someone I can't trust.
    • 1837, L[etitia] E[lizabeth] L[andon], “The Author and the Actress”, in Ethel Churchill: Or, The Two Brides. [], volume III, London: Henry Colburn, [], →OCLC, page 105:
      Lavinia—shrewd, careless, clever; ready to meet any difficulty, however humiliating, that might occur; utterly without principle; confident in that good fortune, which she scrupled at no means of attaining—was the very type of the real.
  4. (physics) A rule or law of nature, or the basic idea on how the laws of nature are applied.
    The Pauli Exclusion Principle prevents two fermions from occupying the same state.
    The principle of the internal combustion engine
    • 2013 July-August, Sarah Glaz, “Ode to Prime Numbers”, in American Scientist, volume 101, number 4:
      Some poems, echoing the purpose of early poetic treatises on scientific principles, attempt to elucidate the mathematical concepts that underlie prime numbers. Others play with primes’ cultural associations. Still others derive their structure from mathematical patterns involving primes.
  5. A fundamental essence, particularly one producing a given quality.
    Many believe that life is the result of some vital principle.
    1. A chemical compound within plant or animal tissue that is characteristic of it and more or less peculiar to it, such that it defines the character of that tissue from a human viewpoint (as for example nicotine in tobacco).
      the active principle
      • 1845, William Gregory, Outlines of Chemistry:
        Cathartine is the bitter, purgative principle of senna.
  6. A source, or origin; that from which anything proceeds; fundamental substance or energy; primordial substance; ultimate element, or cause.
    • 1664, John Tillotson, “Sermon I. The Wisdom of Being Religious. Job XXVIII. 28.”, in The Works of the Most Reverend Dr. John Tillotson, Late Lord Archbishop of Canterbury: [], 8th edition, London: [] T. Goodwin, B[enjamin] Tooke, and J. Pemberton, []; J. Round [], and J[acob] Tonson] [], published 1720, →OCLC:
      The soul of man is an active principle.
  7. An original faculty or endowment.
    • 1828, Dugald Stewart, The Philosophy of the Active and Moral Powers of Man:
      those active principles whose direct and ultimate object is the communication either of enjoyment or suffering
  8. Misspelling of principal.
  9. (obsolete) A beginning.

Usage notes

  • Principle ("moral rule"), as a noun, is often confused with principal, which can be an adjective ("most important") or a noun ("school principal"). A memory aid to avoid this confusion is: "The principal alphabetic principle places A before E". Another well-known one often taught to schoolchildren is that the school principal is their pal (friend).

Derived terms



The translations below need to be checked and inserted above into the appropriate translation tables. See instructions at Wiktionary:Entry layout § Translations.



principle (third-person singular simple present principles, present participle principling, simple past and past participle principled)

  1. (transitive) To equip with principles; to establish, or fix, in certain principles; to impress with any tenet or rule of conduct.

Further reading