What does Irrational mean?

Definitions for Irrational
ɪˈræʃ ə nlir·ra·tional

This dictionary definitions page includes all the possible meanings, example usage and translations of the word Irrational.

Princeton's WordNet

  1. irrational number, irrationaladjective

    a real number that cannot be expressed as a rational number

  2. irrationaladjective

    not consistent with or using reason

    "irrational fears"; "irrational animals"

  3. irrationaladjective

    real but not expressible as the quotient of two integers

    "irrational numbers"


  1. irrationaladjective

    Not according to reason; having no rational basis; clearly contrary to reason; easily disproved by reasoning; absurd; -- of assertions and beliefs. Hence, of actions: foolish; unreasonable.


  1. irrationalnoun

    A real number that can not be expressed as the quotient of two integers, an irrational number.

  2. irrationaladjective

    Not rational; unfounded or nonsensical.

    an irrational decision

  3. irrationaladjective

    Of a real number, that cannot be written as the ratio of two integers.

    The number uE0009599uE001 is irrational.

  4. Etymology: From irrationalis, from ir- + rationalis.

Samuel Johnson's Dictionary

  1. IRRATIONALadjective

    Etymology: irrationalis, Latin.

    Thus began
    Outrage from lifeless things; but discord first,
    Daughter of sin, among th' irrational
    Death introduc'd. John Milton, Paradise Lost.

    He hath eat'n, and lives,
    And knows, and speaks, and reasons and discerns;
    Irrational 'till then. John Milton, Paradise Lost, b. ix.

    Since the brain is only a part transmittent, and that humours oft are precipitated to the lungs before they arrive to the brain, no kind of benefit can be effected from so irrational an application. Gideon Harvey, on Consumptions.

    I shall quietly submit, not wishing so irrational a thing as that every body should be deceived. Alexander Pope.


  1. irrational

    Irrationality is cognition, thinking, talking, or acting without inclusion of rationality. It is more specifically described as an action or opinion given through inadequate use of reason, or through emotional distress or cognitive deficiency. The term is used, usually pejoratively, to describe thinking and actions that are, or appear to be, less useful, or more illogical than other more rational alternatives.Irrational behaviors of individuals include taking offense or becoming angry about a situation that has not yet occurred, expressing emotions exaggeratedly (such as crying hysterically), maintaining unrealistic expectations, engaging in irresponsible conduct such as problem intoxication, disorganization, and falling victim to confidence tricks. People with a mental illness like schizophrenia may exhibit irrational paranoia. These more contemporary normative conceptions of what constitutes a manifestation of irrationality are difficult to demonstrate empirically because it is not clear by whose standards we are to judge the behavior rational or irrational.


  1. irrational

    In mathematics, irrational refers to a type of number that cannot be expressed as a simple fraction or ratio of two integers. It is a number that cannot be written as a/b, where a and b are integers and b ≠ 0. The decimal representation of an irrational number is non-terminating and non-repeating. Common examples of irrational numbers include the square root of 2, Pi, and the golden ratio. In a more broader or general sense outside mathematics, irrational can refer to something that is not logical or not based on reason; describing behavior or actions that lack sound judgement, clear thinking or reasoning.

Webster Dictionary

  1. Irrationaladjective

    not rational; void of reason or understanding; as, brutes are irrational animals

  2. Irrationaladjective

    not according to reason; absurd; foolish

  3. Irrationaladjective

    not capable of being exactly expressed by an integral number, or by a vulgar fraction; surd; -- said especially of roots. See Surd

  4. Etymology: [L. irrationalis: cf. F. irrationnel. See In- not, and Rational.]

Chambers 20th Century Dictionary

  1. Irrational

    ir-rash′un-al, adj. void of reason or understanding: absurd.—n. Irrational′ity.—adv. Irra′tionally.—Irrational numbers, a term applied to those roots of numbers which cannot be accurately expressed by a finite number of figures—e.g. √2 is an irrational number.

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  1. Chaldean Numerology

    The numerical value of Irrational in Chaldean Numerology is: 9

  2. Pythagorean Numerology

    The numerical value of Irrational in Pythagorean Numerology is: 9

Examples of Irrational in a Sentence

  1. Zhang Qi:

    The measure is mainly intended to curb irrational speculation, which could be good for the overall market in the long run, yet could bode ill for speculative stocks in the short term.

  2. Jony Luna:

    We are not crazy, or irrational, as they call us. Our fathers fought when they couldn't even read and write, now it is our time to fight, to defend our people and the people of Bolivia.

  3. Todd Sears:

    Doing good for the LGBT community is a business imperative and does actually impact the bottom line, markets are rational and discrimination like this is irrational. It was never a really hard push to get these Wall Street firms to support this.

  4. Richard Peters:

    He seemed quite clear and lucid, whereas this may seem like very irrational behavior, he didnt appear to me to be facing any challenges or mental impairment, other than holding fairly extreme views.

  5. Andrew Bernstein:

    For the first time in history, the rational and the good are fully armed in the battle against evil. Here we finally find the answer to our paradox; now we can understand the nature of the social power held by evil. Ultimately, the evil, the irrational, truly has no power. The evil men’s control of morality is transient; it lives on borrowed time made possible only by the errors of the good. In time, as more honest men grasp the truth, evil’s stranglehold will be easily broken.

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"Irrational." Definitions.net. STANDS4 LLC, 2024. Web. 18 Jul 2024. <https://www.definitions.net/definition/Irrational>.

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