irrational

[ ih-rash-uh-nl ]

/ ɪˈræʃ ə nl /

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See synonyms for: irrational / irrationally on Thesaurus.com

adjective

without the faculty of reason; deprived of reason.

without or deprived of normal mental clarity or sound judgment.

not in accordance with reason; utterly illogical: irrational arguments.

not endowed with the faculty of reason: irrational animals.

Mathematics.

(of a number) not capable of being expressed exactly as a ratio of two integers.
(of a function) not capable of being expressed exactly as a ratio of two polynomials.

Algebra. (of an equation) having an unknown under a radical sign or, alternately, with a fractional exponent.

Greek and Latin Prosody.

of or relating to a substitution in the normal metrical pattern, especially a long syllable for a short one.
noting a foot or meter containing such a substitution.

noun

Mathematics. irrational number.

OTHER WORDS FOR irrational

3 unreasonable, ridiculous; insensate.

See synonyms for irrational on Thesaurus.com

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Origin of irrational

First recorded in 1425–75; late Middle English word from Latin word irratiōnālis.See ir-², rational

OTHER WORDS FROM irrational

ir·ra·tion·al·ly, adverbir·ra·tion·al·ness, nounnon·ir·ra·tion·al, adjective, nounnon·ir·ra·tion·al·ly, adverb

non·ir·ra·tion·al·ness, noun

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use irrational in a sentence

“None of the status conference orders or decisions on motions were found to be irrational,” said Lucian Chalfen, a spokesman for the Office of Court Administration.
New York Court Officials Complete Rare Review of Cases Handled by Judge Forced Into Retirement by Dementia|by Joe Sexton|November 20, 2020|ProPublica
Republicans are not irrational for spending down their electoral advantage on more temperamentally extreme candidates and ideologically pure policies.
The crisis isn’t too much polarization. It’s too little democracy.|Ezra Klein|November 12, 2020|Vox
The entire GOP strategy for the Georgia Senate elections apparently centers on a belief that Georgia voters are irrational and will rise up in fury because they think they have been wronged — again — by conniving Democrats.
The elites who think MAGA voters are rubes: Republicans|Jennifer Rubin|November 11, 2020|Washington Post
There’s a reason some marketers refer to this quirk of the industry as “irrational budget dumping.”
‘Great position to steal share’: As use-it-or-lose-it ad spending picks up, TikTok emerges as an unlikely beneficiary|Seb Joseph|October 28, 2020|Digiday

Mathematicians usually solve this problem by arranging the rationals in a line and filling the gaps with irrational numbers to create a complete number system that we call the real numbers.
An Infinite Universe of Number Systems|Kelsey Houston-Edwards|October 19, 2020|Quanta Magazine
According to her personal blog, “Irrationally Optimistic,” Zhang is a mother of two, living in a “double professional household.”
Yahoo’s Accused Sexual Harasser Asked Women to Wear More Skirts at Work|Olivia Nuzzi|July 14, 2014|DAILY BEAST
The predominant school of thought holds that the markets are irrationally acting—and crashing—in response to the news.
Let’s All Please Stop Overreacting to Bernanke’s Remarks|Daniel Gross|June 20, 2013|DAILY BEAST
The latest incident will give new life to the gossip that Trierweiler is irrationally jealous of Royal.
France’s Valerie Trierweiler Tweets Against Segolene Royal|Tracy McNicoll|June 12, 2012|DAILY BEAST
It would be better to spend rationally now than irrationally in the heat of an election year.
Larry Summers’ Impossible Stimulus Dream|Zachary Karabell|June 14, 2011|DAILY BEAST
It diminishes what they add to society, irrationally elevating their private lives in ways that do a disservice to them and to us.
Who Cares What Tiger Did?|Conor Friedersdorf|November 28, 2009|DAILY BEAST
The minds of many quite honest men resisted the new knowledge instinctively and irrationally.
The Outline of History: Being a Plain History of Life and Mankind|Herbert George Wells
But the job would take hours, and he was irrationally convinced that Jill had been left behind in the construction camp.
Operation Terror|William Fitzgerald Jenkins
He did not know why he was so irrationally happy, for nothing was changed in his life or hers.
Ethan Frome|Edith Wharton
The elemental mother in her battled on the side of her only son—foolishly, irrationally, unkindly.
Simon the Jester|William J. Locke
They testified that he not only drank himself to death, but that he acted irrationally and was clean out of his mind.
John Marsh's Millions|Charles Klein

British Dictionary definitions for irrational

irrational

/ (ɪˈræʃənəl) /

adjective

inconsistent with reason or logic; illogical; absurd

incapable of reasoning

maths

not rational
(as noun)an irrational

prosody (in Greek or Latin verse)

of or relating to a metrical irregularity, usually the occurrence of a long syllable instead of a short one
denoting a metrical foot where such an irregularity occurs

Derived forms of irrational

irrationally, adverbirrationalness, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

irrational

OTHER WORDS FOR irrational

Origin of irrational

OTHER WORDS FROM irrational

Words related to irrational

How to use irrational in a sentence

British Dictionary definitions for irrational

Derived forms of irrational