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

Example Sentences

Adjective He became irrational as the fever got worse. She had an irrational fear of cats.
Recent Examples on the Web
Adjective
Although deals offered online and in-store have converged in recent years, the fear of missing out on Black Friday still drives sales and sometimes irrational behavior, said Mr. Cohen, who oversaw Sears’s Canadian division before joining Columbia. Imani Moise, WSJ, 24 Nov. 2022 The fear of failure drives some new CISOs toward irrational behavior. Phillimon Zongo, Forbes, 11 Nov. 2022 The irrational behavior of one man has given way to a rise in extremist rhetoric and has led to lives being put in danger. Stephanie Grisham And Gavin J. Smith, CNN, 17 Aug. 2022 Like Jung, Zeltzer believes meaningful coincidences can encourage people to acknowledge the irrational and mysterious. oregonlive, 4 Dec. 2022 Like Jung, Zeltzer believes meaningful coincidences can encourage people to acknowledge the irrational and mysterious. Los Angeles Times, 1 Dec. 2022 And yet, since the spring of 2021, pundits have mocked people who continue to think this way for being irrational and overcautious, and government officials have consistently framed COVID as a matter of personal responsibility. Ed Yong, The Atlantic, 30 Sep. 2022 The institution of hereditary kingship is irrational and impractical, sustained in the present era only through a willful combination of public pageantry and concealed mystery. Rebecca Mead, The New Yorker, 8 Sep. 2022 And that belief that better times are just one more breakthrough away isn’t entirely irrational, given what has happened to America’s tech industry in downturns past. Christopher Mims, WSJ, 29 Oct. 2022
Noun
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 We are all steered by a mixture of the rational and the irrational. Christopher Beha, Harpers Magazine, 5 Jan. 2021 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'irrational.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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 27 Jan. 2023.

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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