irrational

[ ih-rash-uh-nl, -rash-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.

   Synonyms: insensate, ridiculous, unreasonable

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

1. Mathematics. irrational number ( def ).

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

• irˈrationally, adverb
• irˈrationalness, noun

Other Words From

• ir·ra·tion·al·ly adverb
• ir·ra·tion·al·ness noun
• non·ir·ra·tion·al adjective noun
• non·ir·ra·tion·al·ness noun

Word History and Origins

Origin of irrational¹

First recorded in 1425–75; late Middle English, from Latin irratiōnālis; ir- ²( def ), rational ( def )

Example Sentences

You have to strike a balance where you’re not telling people that what they’re saying is irrational, silly, crazy.

From 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.

From Fortune

John Coates, a Wall Street trader turned neuroscientist, considers the molecule of “irrational exuberance” in The Hour Between Dog and Wolf.

From 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.

From Quartz

Only a few months ago, this type of behavior would have been considered excessive, irrational, even pathological, and certainly not healthy.

From No Straight News

The Samaritan guidelines are written around the assumption that suicide is a purely irrational act, an act spurred by illness.

From The Daily Beast

The fact that the virus is still alive has sustained many safety concerns, both rational and irrational, about its use.

From The Daily Beast

The writing team behind these videos are some seriously mad comedy crackheads, and they manage some brilliantly irrational bits.

From The Daily Beast

Farah, of course, is not alone in holding this acrobatically irrational view.

From The Daily Beast

To a certain degree, there is an irrational sense of betrayal.

From The Daily Beast

He was, I knew, a deep, thinly-covered tank of resentments and quite irrational moral rages.

From Project Gutenberg

Suddenly my irrational complaint was silenced as certain words of Saint Paul to the Corinthians reverberated in my mind.

From Project Gutenberg

Animals, irrational animals, had told the secret, and birds of the air had carried the matter.

From Project Gutenberg

It seemed to me that he was foolish and irrational, altogether unlike himself.

From Project Gutenberg

It is an irrational practice, even when adopted by military tribunals.

From Project Gutenberg

Related Words

• aberrant
• absurd
• crazy
• foolish
• incoherent
• insane
• preposterous
• ridiculous
• stupid
• unreasonable
• unsound
• unwise
• wrong