Definition of principle in English:



  • 1A fundamental truth or proposition that serves as the foundation for a system of belief or behaviour or for a chain of reasoning.

    ‘the basic principles of justice’
    • ‘The freedom to make a choice is the basic principle of our democratic world.’
    • ‘The evenly balanced scales of blind justice derive from this principle.’
    • ‘In this introductory article, we lay out some basic principles for understanding complex systems.’
    • ‘The assumption is that these principles of justice underlie any conception of the good.’
    • ‘The challenge to their leadership is to have the courage to support basic democratic principles, only excluding those, who by their actions exclude themselves.’
    • ‘It is a fraternal order whose basic principles are philanthropy, truth and brotherly love.’
    • ‘It is simply not possible to negotiate a political settlement with people who do not understand, or who refuse to accept, basic democratic principles.’
    • ‘It is a fundamental principle in our system of justice that people are treated the same, regardless of their income or status in life, and it is important to uphold that.’
    • ‘Draconian provisions which alter the principles and foundation of our legal system may serve in the long run to undermine that system and give rise to perfidies not initially contemplated.’
    • ‘Following the enlightenment principle of truth through reason alone, it was thought that history cannot be determined until theology has been removed.’
    • ‘But it was only with the publication of Filangieri's great work that a comprehensive reformulation of the nature and underlying principles of the state and of society finally emerged.’
    • ‘There's sense here in going back to some of the basic principles of liberal political philosophy.’
    • ‘What are some of the basic principles and beliefs of Catholicism?’
    • ‘One of the basic principles of a democratic, liberal country is the decentralization of power.’
    • ‘The basic principle for a democratic republic is the independence of the three branches of government executive, legislature and judiciary.’
    • ‘The principles of natural law gained ground, and accompanying them came a growing belief in the equality of all human beings.’
    • ‘In my tale, I set out the metaphysical principles, i.e. principles outside the closed system of the ethics being discussed, on which the ethics are based.’
    • ‘And yet, of course, our principles of fairness and justice must be upheld.’
    • ‘Although its application was inevitably uneven, the Code Napoléon was intended to serve as a universal set of principles founded on reason.’
    • ‘This is a foundation principle of western justice and a basic human right.’
    truth, proposition, concept, idea, theory, postulate
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    1. 1.1usually principles A rule or belief governing one's behaviour.
      ‘struggling to be true to their own principles’
      mass noun ‘she resigned over a matter of principle’
      • ‘If you can forsake your fundamental principles for any reason then you are not the kind of person who can take the country forward.’
      • ‘These principles have governed Snow's approach in growing the family business tenfold since he took the reins in the mid 1980s.’
      • ‘Although some aspects of suicidal behaviour might be interpreted as rational, the behaviour is contrary to basic biological principles of survival.’
      • ‘Rarely have I encountered anyone as passionate and determined in his principles as Donald Bruce, a true patriot and a man who led a remarkable life.’
      • ‘There are three key defining experiences in my life that form the foundation of my principles and beliefs.’
      • ‘But I'm going to speak directly from the heart based on the principles that I believe in.’
      • ‘Law, in the sense of rules and principles that govern human conduct, is a blunt instrument.’
      • ‘Doing what's right appears to be more of a concern for him than for the average person; his platform is strongly governed by his personal principles.’
      • ‘Commonly, the codes will address certain principles, and these will be governed by written rules.’
      morals, morality, moral standards, moral values, ethics, code of ethics, beliefs, credo, ideals, standards, integrity, uprightness, high-mindedness, righteousness, virtue, probity, rectitude, sense of honour, honour, decency, conscience, sense of duty, scruples
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    2. 1.2mass noun Morally correct behaviour and attitudes.
      ‘a man of principle’
      • ‘Seinfeld exposes the human destructiveness and lack of principle and morality that exist to some degree in all people.’
      • ‘For nothing indicates a failure to understand the nature of a moral principle better than to believe that it is capable of enforcing itself.’
      • ‘Money had replaced principles in determining policy.’
      • ‘Prof Southall is a man of great principle and he won't change his mind if he does not think his mind should be changed.’
      • ‘However, in the attempt to unite, there must be no compromise of principle and professional integrity must reign supreme.’
      • ‘Legislation based on principle and evidence will have our support.’
      • ‘To do so is foolish and ill-mannered, invites scorn, and is contrary to the whole principle of the clan system.’
      • ‘Bafflingly, a knighthood still awaits, but this present accolade will surely not be the last that comes the way of a musician of unswerving integrity and principle.’
      • ‘We worked out a position we could adhere to throughout the campaign, one based on principle as well as convenience.’
      • ‘Therefore, ethical action is equated with following rules, principles, laws, maxims, and codes.’
      • ‘I admire and respect him for his repeated and unsung - even derided - demonstrations of integrity and principle.’
      • ‘However, you should not lose heart or compromise over an issue based on principle.’
      • ‘How in one walk of life a person can have such a rigid sense of right and wrong - and in another he can operate with a total disregard for principle, integrity and fair play.’
      • ‘‘I want to bring principle and honour back into politics’ said Jim as he addressed the meeting.’
      • ‘It seems that in situations such as this, politics become incompatible with conscience, principle, decency and self-respect.’
      • ‘At six, he is too young to determine what his own principles are in this regard.’
      • ‘As well as being wrong in principle, it is wrong in terms of club competition.’
      • ‘While people may be sceptical about politicians who moralise, they are anxious to see them display integrity and principle.’
      • ‘He should be a man of principles, a source of good.’
      • ‘But he's clearly a man of principle and unbending honesty - who, at times, can be cruelly insensitive, as when he tells a man he has casually examined that he has a tumour.’
      morals, morality, moral standards, moral values, ethics, code of ethics, beliefs, credo, ideals, standards, integrity, uprightness, high-mindedness, righteousness, virtue, probity, rectitude, sense of honour, honour, decency, conscience, sense of duty, scruples
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  • 2A general scientific theorem or law that has numerous special applications across a wide field.

    • ‘The code uses so called Bayesian networks, a combination of statistical principles, including Bayes Theorem, hence the name.’
    • ‘Quantum chemistry involves the application of the principles of quantum theory to chemistry.’
    • ‘One line of evidence for the holographic principle comes from black hole physics.’
    • ‘Simple physics principles might explain the mysterious magnetic fields that seem to permeate the cosmos.’
    • ‘When Dirac developed the general principles of quantum theory, this democratic equality between different points of view was maintained in the new dynamics that resulted.’
    • ‘Angular momentum, like all other forms of motion, follows the general principle stated in Newton's third law.’
    • ‘Now the general principles on which quantum field theory are based actually allow for many different consistent theories to be constructed.’
    • ‘These connections allowed a broad dissemination not only of principles but especially the application of the methods of scientific management.’
    • ‘In 1748 Maupertuis showed that Newton's laws of motion could be derived by the application of a teleological principle.’
    • ‘Einstein believed that Maxwells theory should, like all other laws of nature obey the principle of relativity.’
    • ‘The uncertainty principle has been successfully used as a key eligibility criterion for large, simple trials.’
    • ‘For example, there's a short film of Dr. Richard Feynman explaining a principle of quantum mechanics called Bell's inequality.’
    • ‘A physical principle called the diffraction limit says that light cannot be used to see or inscribe features that are smaller than half its wavelength.’
    • ‘Guitar pickups work by the principles of magnetic induction.’
    • ‘The application of scientific principles eventually leads to a fair evaluation of the benefits, disadvantages and true effects of every compound.’
    • ‘Accordingly, atomic physics relies on the principles of quantum mechanics to describe the discrete nature of matter at the atomic and subatomic levels.’
    • ‘A working understanding of basic mathematical principles is ideal, but mostly you just need a calculator and the desire to play the stocks and bonds game.’
    • ‘The Heisenberg uncertainty principle dictates that he can measure the bits in only one mode, not both.’
    • ‘Engineering involves the application of scientific and mathematical principles.’
    • ‘Physics has a big advantage here, since the ability to derive interesting conclusions from general principles comes earlier in physics than in other sciences.’
    1. 2.1 A natural law forming the basis for the construction or working of a machine.
      ‘these machines all operate on the same general principle’
      • ‘However, back then, explanations that were given to the general public regarding the actual principle of the flying machine appeared to be quite vague.’
      • ‘He might have used mechanical aids such as Alberti's veil, the various gadgets illustrated by Durer, or other machines following similar principles.’
      • ‘The principles underlying steam power, machine tools, and mass production were less familiar, hence less transparent.’
      • ‘Mbemba designed the machine around the mathematical principle of the sinuskurve, or sine wave.’
      • ‘Yet, that was the age of levers and pulleys, and machines based on mechanical principles were being used as analog computers in many different ways.’
      • ‘He adopted a new basis for hydrostatics, using two principles from his mechanics, and explained for the first time how a heavy beam can be floated in very little water.’
  • 3A fundamental source or basis of something.

    ‘the first principle of all things was water’
    1. 3.1 A fundamental quality determining the nature of something.
      ‘the combination of male and female principles’
      • ‘As sun and moon represent the male and female principles, once again we see the potential for a happy union between you.’
      • ‘In this close relationship the artist occupies a pivotal position, since he is gifted with the ability to recognize divine principles in nature and recreate these in his works.’
      • ‘Keeping any part of the surplus is simply theft and thus violates the moral principle of justice.’
      • ‘Holding the rapt attention of the audience, the duo exemplified the concept of the male and female principles working in harmony and balance in the Universe, unique to Hindu mythology.’
      • ‘Just as the male and female principles complement each other, our views of history also much combine to give a holistic view of the past.’
    2. 3.2Chemistry with adjective An active or characteristic constituent of a substance, obtained by simple analysis or separation.
      ‘the active principle of Spanish fly’
      • ‘The active principle is extracted and purified from plant material for as long as that process remains economically viable compared with chemical synthesis.’
      • ‘The development of purified cardiac glycosides, the active principles of digitalis, has been a distinct step forward in the treatment of diseases of the heart.’
      • ‘Various studies on the active principles of the manchineel tree have shown tigliane phorbol esters to be the likely cause of the severe reactions.’
      • ‘The active principles were identified as baicalein from the first and methyl gallate from the last two plants.’
      • ‘The pungency of pepper is due to the active principles it contains - the volatile oil, piperine, and resin.’


The words principle and principal are pronounced in the same way but they do not have the same meaning. Principle is normally used as a noun meaning ‘a fundamental basis of a system of thought or belief’, as in this is one of the basic principles of democracy. Principal, on the other hand, is normally an adjective meaning ‘main or most important’, as in one of the country's principal cities. Principal can also be a noun, where it is used to refer to the most senior or most important person in an organization or other group: the deputy principal


  • in principle

    • 1As a general idea or plan, although the details are not yet established.

      ‘the government agreed in principle to a peace plan that included a ceasefire’
      • ‘The signatories have agreed on this in principle and now the bartering over the detail continues.’
      • ‘This agreement is only in principle and nothing has been committed to paper yet.’
      • ‘The town council says it supports the plan in principle, but says there could be problems finding a suitable location.’
      • ‘The plan was accepted in principle but the details for it were not.’
      • ‘Councillors agreed to the scheme in principle, with the detail being delegated to planning officers.’
      • ‘Councillors have agreed the sale in principle and the proposals are set to go out to consultation before a final decision is made.’
      • ‘It is understood that agreement has been reached in principle, and that only terms remain to be finalised.’
      • ‘Councillors agreed to recommend the development in principle, subject to funding being found.’
      • ‘Members approved the ideas in principle, and agreed they would like another report on progress in July.’
      • ‘Last month, they said they were mindful to approve the development in principle but wanted amended plans.’
      in general, on balance, generally, in essence, by and large, on the whole, all in all, in the main, all things considered, taking everything into consideration
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      1. 1.1Used to indicate that although something is theoretically possible, in reality it may not actually happen.
        ‘in principle, the banks are entitled to withdraw these loans when necessary’
        • ‘It's right in principle that businesses whose customers cause a mess should be held responsible for clearing it up.’
        • ‘However, he sees no reason to believe that a machine cannot, in principle, do the things humans can do.’
        • ‘That may be a good point in principle but it's an irrelevance in practice.’
        • ‘This all seemed a great idea in principle but of course the numbers don't work.’
        • ‘Electronic voting is a good idea in principle, provided it's done right.’
        • ‘The first test here should be whether infinite computing power is, in principle, even possible.’
        • ‘Although having a smoke free environment seems good in principle, how would it be enforced?’
        • ‘That's why many of us, even though we know it is a good idea in principle, don't have the time or energy to do it.’
        • ‘This is a fine idea in principle, but providing high quality information is expensive.’
        • ‘That the class should fit the pupil rather than vice versa sounds great - in principle.’
        in theory, theoretically, on paper, in an ideal world
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  • on principle

    • Because of or in order to demonstrate one's adherence to a particular belief.

      ‘he refused, on principle, to pay the fine’
      • ‘I could have been in Wyoming and I object on principle to paying £9 for popcorn.’
      • ‘I'm not going to pay up on principle for a ticket I didn't deserve.’
      • ‘If his attack is based on principle, he should be praised.’
      • ‘But I wouldn't go in there now on principle, even if you paid me.’
      • ‘Pittman said he later spoke to an employee who apologized and asked him to keep his subscription, but he quit on principle.’
      • ‘I have never been in a limo in my life and would refuse to do so on principle.’
      • ‘You and I differ here in one aspect, had my employer asked me to take my blog down I, on principle would not have done, whatever the consequences.’
      • ‘He stood on principle and sought historical solutions, but not strategic ones.’
      • ‘Following a ship to the bottom of the sea on principle is seldom a wise choice.’
      • ‘And he supported the Civil Union Bill through its first reading on principle.’


Late Middle English: from Old French, from Latin principium ‘source’, principia (plural) ‘foundations’, from princeps, princip- ‘first, chief’.