rational
Americanadjective
-
agreeable to reason; reasonable; sensible.
a rational plan for economic development.
-
having or exercising reason, sound judgment, or good sense.
a calm and rational negotiator.
- Synonyms:
- sagacious, judicious, wise, intelligent
- Antonyms:
- stupid
-
being in or characterized by full possession of one's reason; sane; lucid.
The patient appeared perfectly rational.
- Antonyms:
- insane
-
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.
-
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
-
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
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Arithmetic
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
The Number System
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
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.
I’d go back to the drawing board on this one and plot out a rational plan for Roth conversions over several years, if that’s what you decide makes the most sense for you.
From MarketWatch • May 26, 2026
Reading a review … it’s something rational that is describing something irrational.
From Los Angeles Times • May 26, 2026
"These disorders manifest in current symptoms of unending, synergistic, and complex delusions that thwart a rational understanding of his imminent execution," his lawyers argued.
From BBC • May 21, 2026
Diamondback appears to be making a rational choice that should pay off as prices stay high during the war, and afterward too as countries rebuild their inventories.
From Barron's • May 5, 2026
If we start with a carpet the size of half an atom, we can cover all the rational numbers on the number line with carpets that, in total, take up less room than an atom.
From "Zero: The Biography of a Dangerous Idea" by Charles Seife
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.
