Definition of irrational in English:

irrational

adjective

  • 1Not logical or reasonable.

    ‘irrational feelings of hostility’
    • ‘By absurd, I do not mean silly, but absurd as is in the illogical or irrational.’
    • ‘I am sort of notorious for my utterly irrational fears.’
    • ‘Booze and cocaine corroded his sanity and left him with a legacy of irrational behaviour.’
    • ‘Their hostility towards each other, however, was tangible and frequently led to quite irrational behaviour.’
    • ‘Solutions that would seem logical to us would seem totally irrational to them.’
    • ‘But Delta's seemingly irrational behavior has a very logical explanation.’
    • ‘She had never known for her daughter to be so irrational, so crazy.’
    • ‘Power sets the guidelines by which we measure what is reasonable and what is irrational.’
    • ‘Without that insight, a supplier can encounter fewer surprises by evaluating even seemingly irrational scenarios.’
    • ‘If it hadn't seemed so irrational, she would have begged him not to go.’
    • ‘Australians aren't at all used to visceral and irrational hatred directed at them.’
    • ‘Chris smiled, sure that Seth's fears were completely irrational.’
    • ‘The more irrational and illogical someone becomes, the more logical and incisive I become.’
    • ‘I believe that the seemingly irrational logic of the national can still promote everyday alliances and popular mobilizations.’
    • ‘Crowds and mobs are not completely irrational, but they have their own logic.’
    • ‘He had a very short fuse and he could be totally irrational at times.’
    • ‘Home values have soared to high levels in many countries as irrational exuberance grips the markets.’
    • ‘Identify and uproot irrational beliefs that lead you to place unrealistic demands on yourself.’
    • ‘The author of the piece argues that our attitude towards it is mostly irrational prejudice.’
    • ‘I have an irrational dislike of cell phones.’
    unreasonable, illogical, groundless, baseless, unfounded, unjustifiable, unsound
    View synonyms
    1. 1.1 Not endowed with the power of reason.
      • ‘Man is an irrational being, morals are irrational, and have no metaphysical foundation which make them "real" or worth paying any attention to.’
      • ‘Whenever you encounter a system that seems so irrational, you should ponder what's going on beneath the surface.’
  • 2Mathematics
    (of a number, quantity, or expression) not expressible as a ratio of two integers, and having an infinite and non-recurring expansion when expressed as a decimal. Examples of irrational numbers are the number π and the square root of 2.

    • ‘How can mathematical concepts like points, infinitesimally small quantities, or irrational numbers be anything but products of our minds?’
    • ‘A transcendental number is an irrational number that is not a root of any polynomial equation with integer coefficients.’
    • ‘He considered computation with irrational numbers and polynomials to be part of algebra.’
    • ‘What about a seed angle derived from the golden ratio, an irrational number?’
    • ‘The square root of 2 is an irrational number because it can't be written as a ratio of two integers.’

noun

Mathematics
  • An irrational number or quantity; a surd.

    • ‘Any finite segment can be continued to produce a rational and any finite segment can be continued to produce an irrational.’
    • ‘His commentary to Euclid is of interest because of its discussion of unordered irrationals.’
    • ‘Whether such quirks in the irregularity of irrationals have any implications for number theory remains an open question for mathematicians.’
    • ‘Eudoxus's definition of equal ratios corresponds exactly to the modern theory of irrationals.’
    • ‘If we chop off an infinite cfe after a finite number of steps then we will create a rational approximation to the original irrational.’

Origin

Late Middle English: from Latin irrationalis, from in- ‘not’ + rationalis (see rational).

Pronunciation

irrational

/ɪˈraʃ(ə)n(ə)l/