irrational

American  

[ih-rash-uh-nl, -rash-nl] / ɪˈræʃ ə nl, -ˈræʃ 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.

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noun

1. Mathematics. irrational number.

irrational British  

/ 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

   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

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Other Word Forms

• irrationally adverb
• irrationalness noun
• nonirrational adjective
• nonirrationalness noun

Etymology

Origin of irrational

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

Example Sentences

“Panic by definition is irrational. Markets don’t know how to price it.”

From The Wall Street Journal

One of them, lawyer Seydou Diagne, called the decision to strip Senegal of their title "so blatant, so absurd, so irrational".

From BBC

However, she said she had experienced fear and irrational guilt after Eliza's diagnosis.

From BBC

“In view of the current robust demand for AI cloud services, we are not concerned that Tencent’s deeper involvement in the AI cloud market would lead to irrational competition.”

From The Wall Street Journal

"The railway is part of the rationalisation of our transport system, especially on the Uganda side, which is irrational and wasteful," the veteran leader told the ceremony.

From Barron's

Related Words

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