irrational

adjective
ir·​ra·​tio·​nal | \ i-ˈra-sh(ə-)nəl How to pronounce irrational (audio) , ˌi(r)-\

Definition of irrational

 (Entry 1 of 2)

: not rational: such as
a(1) : not endowed with reason or understanding
(2) : lacking usual or normal mental clarity or coherence
b : not governed by or according to reason irrational fears

c Greek & 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

irrational

noun

Definition of irrational (Entry 2 of 2)

1 : an irrational being

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Other Words from irrational

Adjective

irrationality \ i-​ˌra-​shə-​ˈna-​lə-​tē How to pronounce irrationality (audio) , ˌi(r)-​ \ noun
irrationally \ i-​ˈra-​sh(ə-​)nə-​lē How to pronounce irrationally (audio) , ˌi(r)-​ \ adverb

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

Rami Nader is a Canadian psychologist who studies coulrophobia, the irrational fear of clowns. Frank T. Mcandrew, Quartzy, "The psychology behind why we find clowns so creepy," 6 Sep. 2019 Dock Ellis, very good Pittsburgh Pirates pitcher, was highly quotable and occasionally irrational. Paul Daugherty, Cincinnati.com, "Doc: Let's go back to when we put baseball cards in our bicycle tires and MLB was king.," 6 July 2019 My obsession with perfection was still all-consuming, and my irrational fears were bleeding into other areas of my life. Alex Daly, Glamour, "This Is What It’s Like to Be Obsessed With Perfection," 13 May 2019 From there, Rees-Mogg’s dictates go from irrational to perverse. Burbank Leader, "A Word, Please: New leader of Britain’s House of Commons imposes unusual grammar rules," 22 Aug. 2019 The aphorism, in the course of history, can be taken as the epitome of the rational or the epitome of the irrational. Adam Gopnik, The New Yorker, "The Art of Aphorism," 15 July 2019 Phobias: Strong, persistent, irrational fear of places, situations, or objects that pose no threat. Kayla Webley Adler, Marie Claire, "Feeling Anxious? So Is Everyone Else. This Guide Will Help.," 8 July 2019 Bush's son previously said his father had been diagnosed with schizo-affective disorder and had expressed irrational fears in the past. Billy Kobin, The Courier-Journal, "Kroger shooting suspect is now competent to stand trial," 27 Oct. 2018 The lawsuit states that medical staff chalked up his irrational behavior to drug use. oregonlive.com, "Family of Portland man who died jogging on I-5 sues hospital for $3 million, claims doctors brushed off his mental crisis," 13 July 2019

Recent Examples on the Web: Noun

Instead, mathematicians ask about the proportion of the total number of irrationals corralled by each fraction. Quanta Magazine, "New Proof Settles How to Approximate Numbers Like Pi," 14 Aug. 2019

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.

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First Known Use of irrational

Adjective

14th century, in the meaning defined above

Noun

1646, in the meaning defined at sense 1

History and Etymology for irrational

Adjective

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

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Statistics for irrational

Last Updated

24 Sep 2019

Look-up Popularity

Time Traveler for irrational

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

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More Definitions for irrational

irrational

adjective

English Language Learners Definition of irrational

: not thinking clearly : not able to use reason or good judgment
: not based on reason, good judgment, or clear thinking

irrational

adjective
ir·​ra·​tio·​nal | \ i-ˈra-shə-nᵊl How to pronounce irrational (audio) \

Kids Definition of irrational

1 : not able to reason The fever made him irrational.
2 : not based on reason irrational fears

Other Words from irrational

irrationally adverb

irrational

adjective
ir·​ra·​tio·​nal | \ (ˈ)ir-ˈ(r)ash-nəl, -ən-ᵊl How to pronounce irrational (audio) \

Medical Definition of irrational

: 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

Other Words from irrational

irrationality \ (ˌ)ir-​ˌ(r)ash-​ə-​ˈnal-​ət-​ē How to pronounce irrationality (audio) \ noun, plural irrationalities
irrationally \ (ˈ)ir-​ˈ(r)ash-​nə-​lē, -​ən-​ᵊl-​ē How to pronounce irrationally (audio) \ adverb

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irrational

adjective
ir·​ra·​tio·​nal | \ ir-ˈra-shə-nəl How to pronounce irrational (audio) \

Legal Definition of irrational

: 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

Other Words from irrational

irrationality \ ir-​ˌra-​shə-​ˈna-​lə-​tē How to pronounce irrationality (audio) \ noun
irrationally adverb

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