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.

Matched Categories

How to pronounce irrational?

How to say irrational in sign language?


  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. Joe Biden:

    The more the walls close in on this guy, the more irrational he becomes.

  2. Yaakov Menken:

    Repeatedly accusing the Jewish state of Israel of ‘genocide,' ‘apartheid,' and other fictitious crimes while praising China, a country that is putting Muslims in internment camps, indicates an irrational hatred of Jews and not a concern for human rights, with regards to Jews, diversity heads seem to share much in common with grand wizards of the Ku Klux Klan, and it is clear that the entire field needs to be reevaluated before more Jewish students are placed at unnecessary risk.

  3. Plato:

    Just as it would be madness to settle on medical treatment for the body of a person by taking an opinion poll of the neighbors, so it is irrational to prescribe for the body politic by polling the opinions of the people at large.

  4. Edgar Allan Poe:

    It is by no means an irrational fancy that, in a future existence, we shall look upon what we think our present existence, as a dream.

  5. Darryl Genovesi:

    It’s irrational day-trading, nothing fundamental. Same as GameStop, Tootsie Roll, Virgin Galactic, etc.

Popularity rank by frequency of use


Translations for irrational

From our Multilingual Translation Dictionary

Get even more translations for irrational »


Find a translation for the irrational definition in other languages:

Select another language:

  • - Select -
  • 简体中文 (Chinese - Simplified)
  • 繁體中文 (Chinese - Traditional)
  • Español (Spanish)
  • Esperanto (Esperanto)
  • 日本語 (Japanese)
  • Português (Portuguese)
  • Deutsch (German)
  • العربية (Arabic)
  • Français (French)
  • Русский (Russian)
  • ಕನ್ನಡ (Kannada)
  • 한국어 (Korean)
  • עברית (Hebrew)
  • Gaeilge (Irish)
  • Українська (Ukrainian)
  • اردو (Urdu)
  • Magyar (Hungarian)
  • मानक हिन्दी (Hindi)
  • Indonesia (Indonesian)
  • Italiano (Italian)
  • தமிழ் (Tamil)
  • Türkçe (Turkish)
  • తెలుగు (Telugu)
  • ภาษาไทย (Thai)
  • Tiếng Việt (Vietnamese)
  • Čeština (Czech)
  • Polski (Polish)
  • Bahasa Indonesia (Indonesian)
  • Românește (Romanian)
  • Nederlands (Dutch)
  • Ελληνικά (Greek)
  • Latinum (Latin)
  • Svenska (Swedish)
  • Dansk (Danish)
  • Suomi (Finnish)
  • فارسی (Persian)
  • ייִדיש (Yiddish)
  • հայերեն (Armenian)
  • Norsk (Norwegian)
  • English (English)

Word of the Day

Would you like us to send you a FREE new word definition delivered to your inbox daily?

Please enter your email address:


Use the citation below to add this definition to your bibliography:


"irrational." Definitions.net. STANDS4 LLC, 2024. Web. 23 Apr. 2024. <https://www.definitions.net/definition/irrational>.

Discuss these irrational definitions with the community:


    Are we missing a good definition for irrational? Don't keep it to yourself...

    Image or illustration of


    Credit »

    Free, no signup required:

    Add to Chrome

    Get instant definitions for any word that hits you anywhere on the web!

    Free, no signup required:

    Add to Firefox

    Get instant definitions for any word that hits you anywhere on the web!

    Browse Definitions.net


    Are you a words master?

    prevent from being seen or discovered
    A aggravate
    B conceal
    C depend
    D distinguish

    Nearby & related entries:

    Alternative searches for irrational: