Definition of irrational in English:

irrational

adjective

  • 1Not logical or reasonable.

    • ‘Without that insight, a supplier can encounter fewer surprises by evaluating even seemingly irrational scenarios.’
    • ‘I believe that the seemingly irrational logic of the national can still promote everyday alliances and popular mobilizations.’
    • ‘Identify and uproot irrational beliefs that lead you to place unrealistic demands on yourself.’
    • ‘Their hostility towards each other, however, was tangible and frequently led to quite irrational behaviour.’
    • ‘The more irrational and illogical someone becomes, the more logical and incisive I become.’
    • ‘Power sets the guidelines by which we measure what is reasonable and what is irrational.’
    • ‘Home values have soared to high levels in many countries as irrational exuberance grips the markets.’
    • ‘Booze and cocaine corroded his sanity and left him with a legacy of irrational behaviour.’
    • ‘Solutions that would seem logical to us would seem totally irrational to them.’
    • ‘Chris smiled, sure that Seth's fears were completely irrational.’
    • ‘He had a very short fuse and he could be totally irrational at times.’
    • ‘Crowds and mobs are not completely irrational, but they have their own logic.’
    • ‘But Delta's seemingly irrational behavior has a very logical explanation.’
    • ‘I am sort of notorious for my utterly irrational fears.’
    • ‘The author of the piece argues that our attitude towards it is mostly irrational prejudice.’
    • ‘If it hadn't seemed so irrational, she would have begged him not to go.’
    • ‘I have an irrational dislike of cell phones.’
    • ‘Australians aren't at all used to visceral and irrational hatred directed at them.’
    • ‘By absurd, I do not mean silly, but absurd as is in the illogical or irrational.’
    • ‘She had never known for her daughter to be so irrational, so crazy.’
    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 nonrecurring 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?’
    • ‘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.’
    • ‘He considered computation with irrational numbers and polynomials to be part of algebra.’
    • ‘A transcendental number is an irrational number that is not a root of any polynomial equation with integer coefficients.’

noun

Mathematics
  • An irrational number.

    • ‘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.’
    • ‘Any finite segment can be continued to produce a rational and any finite segment can be continued to produce an irrational.’
    • ‘Whether such quirks in the irregularity of irrationals have any implications for number theory remains an open question for mathematicians.’
    • ‘His commentary to Euclid is of interest because of its discussion of unordered irrationals.’

Origin

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

Pronunciation

irrational

/ɪ(r)ˈræʃ(ə)nəl//i(r)ˈraSH(ə)nəl/