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This page has 10 definitions of rational in English and German. Rational is an adjective and noun. Examples of how to use rational in a sentence are shown. Also define these 27 related words and terms: reasoning, logical, sound, contradictory, absurd, healthy, balance, intellect, reasonableness, mathematics, arithmetic, number theory, ratio, integer, algebraic, polynomial, chemistry, compound, graphic, formula, physics, physical, object, rational number, number, quotient, and breastplate.

See also: rațional


Alternative forms


Etymology 1

From Old French rationel, rational, from Latin rationalis (of or belonging to reason, rational, reasonable; having a ratio), from ratio (reason; calculation).


rational (comparative more rational, superlative most rational)

  1. Capable of reasoning.
    Man is a rational creature.
    • 2001, Mark Sainsbury, chapter 1, in Logical Forms — An Introduction to Philosophical Logic, 2nd edition, Blackwell Publishing, →ISBN, §7, page 32:
      The utility of valid arguments is a monument to our frailty: to the fact that we are not completely rational beings.
  2. Logically sound; not contradictory or otherwise absurd.
    His statements were quite rational.
  3. (of a person or personal characteristics) Healthy or balanced intellectually; exhibiting reasonableness.
    rational conduct
    • 2014 June 21, “Magician’s brain”, in The Economist, volume 411, number 8892:
      The [Isaac] Newton that emerges from the [unpublished] manuscripts is far from the popular image of a rational practitioner of cold and pure reason. The architect of modern science was himself not very modern. He was obsessed with alchemy.
  4. (mathematics, arithmetic, number theory, not comparable) Of a number, capable of being expressed as the ratio of two integers.
    ¾ is a rational number, but √2 is an irrational number.
    • Integer definition
      English Wikipedia has an article on:
      A number that is not a fraction; an element of the infinite and numerable set {..., -3, -2, -1, 0, 1, 2, 3, ...}.
  5. (mathematics, arithmetic, not comparable) Of an algebraic expression, capable of being expressed as the ratio of two polynomials.
  6. (chemistry) Expressing the type, structure, relations, and reactions of a compound; graphic; said of formulae.
    • Chemistry definition
      The branch of natural science that deals with the composition and constitution of substances and the changes that they undergo as a consequence of alterations in the constitution of their molecules. (1 of 3 chemistry definitions)
  7. (physics) Expressing a physical object.
    A rational table is physical, a written table is neither.
Related terms


rational (plural rationals)

  1. (mathematics) A rational number: a number that can be expressed as the quotient of two integers.
    The quotient of two rationals is again a rational.

Etymology 2

From Old French rational, from Medieval Latin rationale (a pontifical stole, a pallium, an ornament worn over the chasuble), neuter of Latin rationalis (rational), for which see the first etymology. Translation of λογεῖον (logeîon) or perhaps λόγιον (lógion, oracle) in the Septuagint version of Exodus 28.


rational (plural rationals)

  1. (historical) The breastplate worn by Israelite high priests.


Further reading

  • "rational" in Raymond Williams, Keywords (revised), 1983, Fontana Press, page 252.




From Latin rationalis.


  • IPA(key): [ˌʁat͡si̯oˈnaːl]
  • Hyphenation: ra‧ti‧o‧nal
  • (file)


rational (comparative rationaler, superlative am rationalsten)

  1. rational


Further reading