[rash-uh-nl, rash-nl]
See more synonyms for rational on Thesaurus.com
  1. agreeable to reason; reasonable; sensible: a rational plan for economic development.
  2. having or exercising reason, sound judgment, or good sense: a calm and rational negotiator.
  3. being in or characterized by full possession of one's reason; sane; lucid: The patient appeared perfectly rational.
  4. endowed with the faculty of reason: rational beings.
  5. of, relating to, or constituting reasoning powers: the rational faculty.
  6. proceeding or derived from reason or based on reasoning: a rational explanation.
  7. Mathematics.
    1. capable of being expressed exactly by a ratio of two integers.
    2. (of a function) capable of being expressed exactly by a ratio of two polynomials.
  8. Classical Prosody. capable of measurement in terms of the metrical unit or mora.
  1. Mathematics. rational number.

Origin of rational

1350–1400; Middle English racional < Latin ratiōnālis, equivalent to ratiōn- (stem of ratiō) reason + -ālis -al1
Related formsra·tion·al·ly, adverbra·tion·al·ness, nounan·ti·ra·tion·al, adjectivean·ti·ra·tion·al·ly, adverbhy·per·ra·tion·al, adjectivehy·per·ra·tion·al·ly, adverbnon·ra·tion·al, adjectivenon·ra·tion·al·ly, adverbo·ver·ra·tion·al, adjectiveo·ver·ra·tion·al·ly, adverbpre·ra·tion·al, adjectivequa·si-ra·tion·al, adjectivequa·si-ra·tion·al·ly, adverbtrans·ra·tion·al, adjectivetrans·ra·tion·al·ly, adverbul·tra·ra·tion·al, adjectiveul·tra·ra·tion·al·ly, adverbun·ra·tion·al, adjectiveun·ra·tion·al·ly, adverb
Can be confusedrational reasonable (see synonym study at reasonable)

Synonyms for rational

See more synonyms for on Thesaurus.com
2. intelligent, wise, judicious, sagacious, enlightened. 6. See reasonable.

Antonyms for rational

2. stupid. 3. insane.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for rationally

reasonably, intelligently, wisely, logically, judiciously, lucidly

Examples from the Web for rationally

Contemporary Examples of rationally

Historical Examples of rationally

British Dictionary definitions for rationally


  1. using reason or logic in thinking out a problem
  2. in accordance with the principles of logic or reason; reasonable
  3. of sound mind; sanethe patient seemed quite rational
  4. endowed with the capacity to reason; capable of logical thoughtman is a rational being
  5. maths expressible as a ratio of two integers or polynomialsa rational number; a rational function
  1. maths a rational number
Derived Formsrationally, adverbrationalness, noun

Word Origin for rational

C14: from Latin ratiōnālis, from ratiō reason
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for rationally



late 14c., "pertaining to reason;" mid-15c., "endowed with reason," from Old French racionel and directly from Latin rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason" (see ratio).

Online Etymology Dictionary, © 2010 Douglas Harper

rationally in Medicine


  1. Having or exercising the ability to reason.
  2. Influenced by reasoning rather than by emotion.
  3. Of sound mind; sane.
  4. Based on scientific knowledge or theory rather than practical observation.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.