Main Entry:

¹ir·ra·tio·nal

Pronunciation:

\i-ˈra-sh(ə-)nəl, ˌi(r)-\

Function:

adjective

Etymology:

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

Date:

14th century

: not rational: 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> cGreek & 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>

— ir·ra·tio·nal·i·ty \-ˌra-shə-ˈna-lə-tē\ noun

— ir·ra·tio·nal·ly \-ˈra-sh(ə-)nə-lē\ adverb