irrational

adjective

ir·ra·tio·nal | \ i-ˈra-sh(ə-)nəl

, 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

2 : irrational number

Other Words from irrational Synonyms & Antonyms Example Sentences Learn More about irrational

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Other Words from irrational

Adjective

irrationality \ i-ˌra-shə-ˈna-lə-tē

, ˌi(r)- \ noun

irrationally \ i-ˈra-sh(ə-)nə-lē

, 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.