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irrational

[ih-rash-uh-nl] /ɪˈræʃ ə nl/
adjective
1.
without the faculty of reason; deprived of reason.
2.
without or deprived of normal mental clarity or sound judgment.
3.
not in accordance with reason; utterly illogical:
irrational arguments.
4.
not endowed with the faculty of reason:
irrational animals.
5.
Mathematics.
  1. (of a number) not capable of being expressed exactly as a ratio of two integers.
  2. (of a function) not capable of being expressed exactly as a ratio of two polynomials.
6.
Algebra. (of an equation) having an unknown under a radical sign or, alternately, with a fractional exponent.
7.
Greek and Latin Prosody.
  1. of or relating to a substitution in the normal metrical pattern, especially a long syllable for a short one.
  2. noting a foot or meter containing such a substitution.
noun
8.
Mathematics, irrational number.
Origin
late Middle English
1425-1475
1425-75; late Middle English < Latin irratiōnālis. See ir-2, rational
Related forms
irrationally, adverb
irrationalness, noun
nonirrational, adjective, noun
nonirrationally, adverb
nonirrationalness, noun
Synonyms
3. unreasonable, ridiculous; insensate.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples from the web for irrational
  • Though seemingly irrational, this pattern of faculty politics is familiar to anyone who has worked in a university.
  • It seems irrational to feel the trees closing behind you, as if the forest is cutting you off from the present.
  • Bright's courage was almost as irrational as that of the rebels themselves.
  • It's time to rein in the irrational exuberance of those who raise political money.
  • Unfortunately, almost any argument in favor of nuclear weapons today is likely to be seen as irrational or worse.
  • Please do your research before making such sweeping, totally irrational statements.
  • But those of us with memories that extend to the previous millennium do detect a bit of irrational exuberance.
  • While certainly tragic, it was far from irrational: it turns out the behavioral economics were stacked against them.
  • Suits are a bizarre intrusion from an irrational world.
  • One of the trickiest problems in dealing with an uncertain future is people's seemingly irrational response to it.
British Dictionary definitions for irrational

irrational

/ɪˈræʃənəl/
adjective
1.
inconsistent with reason or logic; illogical; absurd
2.
incapable of reasoning
3.
(maths)
  1. not rational
  2. (as noun): an irrational
4.
(prosody, in Greek or Latin verse)
  1. of or relating to a metrical irregularity, usually the occurrence of a long syllable instead of a short one
  2. denoting a metrical foot where such an irregularity occurs
Derived Forms
irrationally, adverb
irrationalness, 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
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Word Origin and History for irrational
adj.

late 15c., "not endowed with reason" (of beats, etc.); earlier (of quantities) "inexpressible in ordinary numbers" (late 14c.); from Latin irrationalis "without reason," from assimilated form of in- "not, opposite of" (see in- (1)) + rationalis "reason" (see rational). Meaning "illogical, absurd" is attested from 1640s. Related: Irrationally.

Online Etymology Dictionary, © 2010 Douglas Harper
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irrational in Medicine

irrational ir·ra·tion·al (ĭ-rāsh'ə-nəl)
adj.
Not rational; marked by a lack of accord with reason or sound judgment.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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