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 )

Related Words

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