rational Meaning, Definition & Usage

  1. noun an integer or a fraction
    rational number.
  2. adjective consistent with or based on or using reason
    • rational behavior
    • a process of rational inference
    • rational thought
  3. adjective satellite of or associated with or requiring the use of the mind
    noetic; intellectual.
    • intellectual problems
    • the triumph of the rational over the animal side of man
  4. adjective capable of being expressed as a quotient of integers
    • rational numbers
  5. adjective satellite having its source in or being guided by the intellect (as distinguished from experience or emotion)
    • a rational analysis


Ra"tion*al adjective
L. rationalis: cf. F. rationnel. See Ratio, Reason, and cf. Rationale.
  1. Relating to reason; not physical; mental.
    Moral philosophy was his chiefest end; for the rational, the natural, and mathematics . . . were but simple pastimes in comparison of the other. Sir T. North.
  2. Having reason, or the faculty of reasoning; endowed with reason or understanding; reasoning.
    It is our glory and happiness to have a rational nature. Law.
  3. Agreeable to reason; not absurd, preposterous, extravagant, foolish, fanciful, or the like; wise; judicious; as, rational conduct; a rational man.
  4. (Chem.) Expressing the type, structure, relations, and reactions of a compound; graphic; -- said of formulæ. See under Formula. rational drug design. Syn. -- Sane; sound; intelligent; reasonable; sensible; wise; discreet; judicious. -- Rational, reasonable. Rational has reference to reason as a faculty of the mind, and is opposed to traditional; as, a rational being, a rational state of mind, rational views, etc. In these cases the speculative reason is more particularly, referred to. Reasonable has reference to the exercise of this faculty for practical purposes, and means, governed or directed by reason; as, reasonable prospect of success.
    What higher in her society thou find'st Attractive, human, rational, love still. Milton.
    A law may be reasonable in itself, although a man does not allow it, or does not know the reason of the lawgivers. Swift.
Ra"tion*al noun
  1. A rational being. Young.

Webster 1913