1

irrational

adjective ir·ra·tio·nal \ i-ˈra-sh(ə-)nəl , ˌi(r)- \

Definition of irrational

:not rational: such as
a (1) :not endowed with reason or understanding
(2) :lacking usual or normal mental clarity or coherence
b :not governed by or according to reason
  • irrational fears
c Greek & Latin prosody
(1) of a syllable :having a quantity other than that required by the meter
(2) of a foot :containing such a syllable
d (1) :being an irrational number
  • an irrational root of an equation
(2) :having a numerical value that is an irrational number
  • a length that is irrational

irrationality

play \i-ˌra-shə-ˈna-lə-tē, ˌi(r)-\ noun

irrationally

play \i-ˈra-sh(ə-)nə-lē, ˌi(r)-\ adverb

Examples of irrational in a Sentence

  1. He became irrational as the fever got worse.

  2. She had an irrational fear of cats.

Recent Examples of irrational from the Web

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Origin and Etymology of irrational

Middle English, from Latin irrationalis, from in- + rationalis rational

2

irrational

noun

Definition of irrational

1 :an irrational being

First Known Use of irrational

1646


IRRATIONAL Defined for English Language Learners

irrational

adjective

Definition of irrational for English Language Learners

  • : not thinking clearly : not able to use reason or good judgment

  • : not based on reason, good judgment, or clear thinking


IRRATIONAL Defined for Kids

irrational

adjective ir·ra·tio·nal \ i-ˈra-shə-nᵊl \

Definition of irrational for Students

1 :not able to reason
  • The fever made him irrational.
2 :not based on reason
  • irrational fears

irrationally

adverb

Medical Dictionary

irrational

adjective ir·ra·tio·nal \ (ˈ)ir-ˈ(r)ash-nəl, -ən-ᵊl \

medical Definition of irrational

:not rational: as
a :lacking usual or normal mental clarity or coherence
  • was irrational for several days after the accident
b :not governed by or according to reason
  • irrational fears

irrationality

play \(ˌ)ir-ˌ(r)ash-ə-ˈnal-ət-ē\ noun plural -ties

irrationally

play \(ˈ)ir-ˈ(r)ash-nə-lē, -ən-ᵊl-ē\ adverb

Law Dictionary

irrational

adjective ir·ra·tio·nal \ ir-ˈra-shə-nəl \

legal Definition of irrational

:not rational: as
a :not governed by reason, mental clarity, or understanding
b :not governed by a fair consideration of facts or evidence; broadly :arbitrary
  • an irrational decision to deny the permit

irrationality

play \ir-ˌra-shə-ˈna-lə-tē\ noun

irrationally

adverb


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