rational
Americanadjective
-
agreeable to reason; reasonable; sensible.
a rational plan for economic development.
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having or exercising reason, sound judgment, or good sense.
a calm and rational negotiator.
- Synonyms:
- sagacious, judicious, wise, intelligent
- Antonyms:
- stupid
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being in or characterized by full possession of one's reason; sane; lucid.
The patient appeared perfectly rational.
- Antonyms:
- insane
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endowed with the faculty of reason.
rational beings.
-
of, relating to, or constituting reasoning powers.
the rational faculty.
-
proceeding or derived from reason or based on reasoning.
a rational explanation.
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Mathematics.
-
capable of being expressed exactly by a ratio of two integers.
-
(of a function) capable of being expressed exactly by a ratio of two polynomials.
-
-
Classical Prosody. capable of measurement in terms of the metrical unit or mora.
noun
adjective
-
using reason or logic in thinking out a problem
-
in accordance with the principles of logic or reason; reasonable
-
of sound mind; sane
the patient seemed quite rational
-
endowed with the capacity to reason; capable of logical thought
man is a rational being
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maths expressible as a ratio of two integers or polynomials
a rational number; a rational function
noun
Synonym Usage
See reasonable.
Other Word Forms
Derived Forms
Etymology
Origin of rational
First recorded in 1350–1400; Middle English racional, from Latin ratiōnālis, equivalent to ratiōn- (stem of ratiō ) reason + -ālis -al 1
Explanation
Use the adjective rational to describe people or ideas that operate according to logic or reason. While your brother has an artistic temperament, you have a rational one. Rational comes from the Latin word rationalis, meaning reasonable or logical. If you're rational, you do things based on logic, as opposed to impulse or whimsy. The original meaning in English was of something endowed with the ability to reason. Before we knew how smart some animals like dolphins are, writers liked to distinguish rational human minds from the supposedly irrational, instinctual minds of animals.
Vocabulary lists containing rational
Positive Adjectives to Describe People
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Arithmetic
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The Number System
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The idea that valuing this in a rational way for tax purposes is somehow too hard is an insult to our intelligence.
From MarketWatch • Jun. 5, 2026
Raymond James analyst Melissa Fairbanks raised Micron’s price target to $1,100 from $530, citing unprecedented demand and rational capacity additions.
From Barron's • Jun. 2, 2026
And the court continues to conduct itself as though Trump is a rational actor who will hear a no as a no.
From Slate • Jun. 1, 2026
I caught the bug not by reading code but by noticing that the output didn’t match how a rational retiree should behave.
From The Wall Street Journal • May 31, 2026
The rational part of her knew this was hopeless.
From "The House of Hades" by Rick Riordan
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
