rational
Americanadjective
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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.
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of, relating to, or constituting reasoning powers.
the rational faculty.
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proceeding or derived from reason or based on reasoning.
a rational explanation.
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Mathematics.
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capable of being expressed exactly by a ratio of two integers.
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(of a function) capable of being expressed exactly by a ratio of two polynomials.
-
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Classical Prosody. capable of measurement in terms of the metrical unit or mora.
noun
adjective
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using reason or logic in thinking out a problem
-
in accordance with the principles of logic or reason; reasonable
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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
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.
At the same time, your brain’s amygdala, or fear and emotion center, calms down and its prefrontal cortex, which governs rational thought, amps up.
From The Wall Street Journal • Jun. 27, 2026
He added: "Her conclusions are rational and supported by proper, adequate and intelligible reasons."
From BBC • Jun. 23, 2026
So a lot of people think bubbles are an ideological thing, instead of a material thing with reasons and motives that are totally rational — and that we can short-circuit.
From Salon • Jun. 22, 2026
Spreads should be wider than normal to add another level of dealer protection as the market mob is anticipated to make decisions that are unmoored from rational analysis.
From Barron's • Jun. 10, 2026
Some brows creased as rational minds grappled with this proof of the impossible—or at least the hitherto inconceivable.
From "Strange the Dreamer" by Laini Taylor
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.
