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

QUIZ

THINGAMABOB OR THINGUMMY: CAN YOU DISTINGUISH BETWEEN THE US AND UK TERMS IN THIS QUIZ?

Do you know the difference between everyday US and UK terminology? Test yourself with this quiz on words that differ across the Atlantic.

Question 1 of 7

In the UK, COTTON CANDY is more commonly known as…

candystring

candyfloss

candypuff

TAKE THE QUIZ TO FIND OUT

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

Words nearby irrational

irradiance, irradiant, irradiate, irradiation, irradicable, irrational, irrationalism, irrationality, irrationalize, irrational number, Irrawaddy

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

How to use irrational in a sentence

You have to strike a balance where you’re not telling people that what they’re saying is irrational, silly, crazy.
Mobilizing the National Guard Doesn’t Mean Your State Is Under Martial Law. Usually.|by Logan Jaffe|September 17, 2020|ProPublica
It’s possible that today’s market is an indication of things to come, where fundamentals play a larger part in valuations, as opposed to the irrational exuberance that has persisted in recent months within tech.
Jittery investors eye today’s big jobs report as markets rebound from an epic sell-off|Bernhard Warner|September 4, 2020|Fortune
John Coates, a Wall Street trader turned neuroscientist, considers the molecule of “irrational exuberance” in The Hour Between Dog and Wolf.
The best books, journalists, and academics for keeping up with bubbles and trading|John Detrixhe|August 30, 2020|Quartz
Primarily, this problem is a byproduct of “irrational exuberance” in the early 2000s and the use of public sector banks by successive governments to propel the economy.
The Modi government’s plan to overcome economic slump ignores a bitter lesson from the past|Prathamesh Mulye|August 18, 2020|Quartz

Only a few months ago, this type of behavior would have been considered excessive, irrational, even pathological, and certainly not healthy.
Are We All OCD Now, With Obsessive Hand-Washing And Technology Addiction?|LGBTQ-Editor|June 15, 2020|No Straight News
The Samaritan guidelines are written around the assumption that suicide is a purely irrational act, an act spurred by illness.
Cover-Ups and Concern Trolls: Actually, It's About Ethics in Suicide Journalism|Arthur Chu|January 3, 2015|DAILY BEAST
The fact that the virus is still alive has sustained many safety concerns, both rational and irrational, about its use.
Powdered Measles Vaccine Could Be Huge for Developing World|Kent Sepkowitz|December 2, 2014|DAILY BEAST
The writing team behind these videos are some seriously mad comedy crackheads, and they manage some brilliantly irrational bits.
There Are More 'Too Many Cooks' Where That First Fever Dream Came From|Kevin Fallon|November 11, 2014|DAILY BEAST
Farah, of course, is not alone in holding this acrobatically irrational view.
Surprise! Leading ‘Birther’ Thinks Earth is 6,000 Years Young|Asawin Suebsaeng|October 26, 2014|DAILY BEAST
To a certain degree, there is an irrational sense of betrayal.
Renee Zellweger's Face Gets More Medical Scrutiny Than Ebola|Emily Shire|October 21, 2014|DAILY BEAST
He was, I knew, a deep, thinly-covered tank of resentments and quite irrational moral rages.
The New Machiavelli|Herbert George Wells
Suddenly my irrational complaint was silenced as certain words of Saint Paul to the Corinthians reverberated in my mind.
The Relief of Mafeking|Filson Young
Animals, irrational animals, had told the secret, and birds of the air had carried the matter.
The Fortunes of Nigel|Sir Walter Scott
It seemed to me that he was foolish and irrational, altogether unlike himself.
Paul Patoff|F. Marion Crawford
It is an irrational practice, even when adopted by military tribunals.
My Recollections of Lord Byron|Teresa Guiccioli

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 nearby irrational

Words related to irrational

How to use irrational in a sentence

British Dictionary definitions for irrational

Derived forms of irrational