irrational

1 of 2

adjective

ir·​ra·​tio·​nal i-ˈra-sh(ə-)nəl How to pronounce irrational (audio)
ˌi(r)-
: not rational: such as
a(1)
: lacking usual or normal mental clarity or coherence
(2)
: not endowed with reason or understanding
b
: not governed by or according to reason
irrational fears
c Greek and Latin prosody
(1)
of a syllable : having a quantity other than that required by the meter
(2)
of a foot : containing such a syllable
d(1)
: being an irrational number
an irrational root of an equation
(2)
: having a numerical value that is an irrational number
a length that is irrational
irrationality noun
irrationally adverb

irrational

2 of 2

noun

1
: an irrational being
2

Examples of irrational in a Sentence

Adjective He became irrational as the fever got worse. She had an irrational fear of cats.
Recent Examples on the Web
Adjective
Saddam’s behavior after the Gulf War was dangerously provocative and irrational. Gideon Rose, Foreign Affairs, 20 Feb. 2024 In a brief, Ahlers argued the board disregarded evidence of innocence and drew irrational conclusions. Darcy Costello, Baltimore Sun, 19 Jan. 2024 At least if the next few months are any indication, and if your sweet tooth involves sci-fi and an irrational craving for Timothée Chalamet, Zendaya and Austin Butler — all of whom happen to co-star in the season’s biggest movie, as well as a few others. Ann Hornaday, Kansas City Star, 24 Feb. 2024 The constant barrage of self-doubt and the irrational fear of being exposed as a fraud can be suffocating, casting a shadow over your true abilities and potential. Mark Travers, Forbes, 22 Feb. 2024 And because the hatred is irrational, there’s no rational way for Mahomes herself to contradict it. Kathleen Walsh, Glamour, 11 Feb. 2024 And, of course, bad ideas and irrational exuberance are par for the course at CES. Robert Evans, Rolling Stone, 27 Jan. 2024 Pushing them into receiving irreversible medical interventions is irrational and cruel. Ian Kingsbury, National Review, 9 Jan. 2024 Challenge irrational beliefs that contribute to the fear of failure. Colleen Reilly, Forbes, 13 Feb. 2024
Noun
The book comprises portraits of healers, including W. H. R. Rivers, who treated soldiers who suffered from shell shock during the First World War, and Paul Robeson, who found solace in intuition and in the irrational. Condé Nast, The New Yorker, 17 July 2023 But riveted mankind is hopelessly addicted to the irrational, with reliably disastrous results, planetwide. Alison Fishburn, Longreads, 17 Sep. 2022 On the back of the acquisitions of AirTerra and Quiet Logistics in 2021, AEO seemed to do the irrational by bringing onstream capacities and capabilities that significantly exceeded its own item demand. Niall Murphy, Forbes, 17 June 2022 The moral, social, and epistemic void in which Germans found themselves after defeat was filled, at least for a time, by the irrational. Richard J. Evans, The New Republic, 1 Dec. 2021 As such, any attempt to explain it will run sooner or later into the wall of the irrational. Phil Klay, Harper's Magazine, 23 Nov. 2021 But feeling anxious right now is not at all out of line or irrational. Jessica Dulong, CNN, 31 Aug. 2021 Attempting to appease the loudest to the detriment of the community only emboldens the irrational and silences those looking to have productive conversation. Benjamin Ayanian, Star Tribune, 5 May 2021 To believe in the return of a long-dead child reflects the anguish of the believer and, of course, a tendency to embrace the irrational. Dorothy Rabinowitz, WSJ, 29 Apr. 2021

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'irrational.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Adjective

Middle English, from Latin irrationalis, from in- + rationalis rational

First Known Use

Adjective

14th century, in the meaning defined above

Noun

1646, in the meaning defined at sense 1

Time Traveler
The first known use of irrational was in the 14th century

Dictionary Entries Near irrational

Cite this Entry

“Irrational.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/irrational. Accessed 18 Mar. 2024.

Kids Definition

irrational

adjective
ir·​ra·​tio·​nal
(ˈ)ir-ˈ(r)ash-nəl,
-ən-ᵊl
1
: unable to reason
irrational beasts
irrational from fever
2
: not based on reason
irrational fear
3
: being an irrational number
an irrational root of an equation
irrationality
(ˌ)ir-ˌ(r)ash-ə-ˈnal-ət-ē
noun
irrationally
(ˈ)ir-ˈ(r)ash-nə-lē
-ən-ᵊl-ē
adverb

Medical Definition

irrational

adjective
ir·​ra·​tio·​nal (ˈ)ir-ˈ(r)ash-nəl, -ən-ᵊl How to pronounce irrational (audio)
: not rational: as
a
: lacking usual or normal mental clarity or coherence
was irrational for several days after the accident
b
: not governed by or according to reason
irrational fears
irrationality noun
plural irrationalities

Legal Definition

irrational

adjective
ir·​ra·​tio·​nal ir-ˈra-shə-nəl How to pronounce irrational (audio)
: not rational: as
a
: not governed by reason, mental clarity, or understanding
b
: not governed by a fair consideration of facts or evidence
broadly : arbitrary
an irrational decision to deny the permit
irrationality noun
irrationally adverb

More from Merriam-Webster on irrational

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