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

• irˈrationalness, noun
• irˈrationally, adverb

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

Kat McNamara, an independent politician who opposed the bill, told the crowd: "The idea that in order to support a 10-year-old you have to criminalise them is irrational, ineffective and morally bankrupt."

From BBC

She recalled Upton saying irrational things on the phone, like describing seeing relatives who were thousands of miles away.

From Los Angeles Times

That creates a permission structure for unstable people to wallow in their irrational hatreds.

From Salon

“We contracted a syndrome psychologists call irrational antagonism. That is, we split into two groups of four. A power struggle over the project’s direction made things much worse.”

From Los Angeles Times

The finding was overturned by the Police Appeals Tribunal which found the original decision was "irrational" and "inconsistent".

From BBC

Related Words

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