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

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
The list is long, but two of the frontrunners include possessing an irrational phobia of the banana (never had one, never will) and being an abysmal sight reader. Daniel Kohn, SPIN, 26 June 2024 Smart Skills Eric Weinstein: ‘Mental sandboxes’ can help humanity reach new heights Your mind is built to process contradictory, irrational ideas. Big Think, 24 June 2024
Noun
The book comprises portraits of healers, including W. H. R. Rivers, who treated soldiers who suffered from shell shock during the First World War, and Paul Robeson, who found solace in intuition and in the irrational. Condé Nast, The New Yorker, 17 July 2023 But riveted mankind is hopelessly addicted to the irrational, with reliably disastrous results, planetwide. Alison Fishburn, Longreads, 17 Sep. 2022 See all Example Sentences for irrational 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'irrational.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

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 13 Jul. 2024.

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

Last Updated: - Updated example sentences
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