rational

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adjective ra·tio·nal \ ˈrash-nəl , ˈra-shə-nᵊl \

Definition of rational

1 a :having reason or understanding

b :relating to, based on, or agreeable to reason :reasonable

a rational explanation

rational behavior

2 :involving only multiplication, division, addition, and subtraction and only a finite number of times

3 :relating to, consisting of, or being one or more rational numbers

a rational root of an equation

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rationally

adverb

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rationalness

noun

See rational defined for English-language learners

See rational defined for kids

Examples of rational in a Sentence

human beings are rational creatures
insisted there was a rational explanation for the strange creaking noises and that there were no such things as ghosts

Recent Examples of rational from the Web

Rational Vaccines was established in February 2015 and the company entered into its patent agreement with the university later that year, Fernández said.

— marisa taylor, Kaiser Health News, "Offshore Human Testing Of Herpes Vaccine Stokes Debate Over U.S. Safety Rules," 28 Aug. 2017
In another experiment, the study subjects took a test to measure their thinking style on a scale from experiential (a more freewheeling, impulsive thought process) to rational (careful, analytical).

— amitha kalaichandran, The Cut, "Touchscreens Turn You Into a More Impulsive Shopper," 25 Aug. 2017
Shock is a rational response to any domestic terrorist attack.

— joshua adams, Longreads, "What Thomas Jefferson Taught Me About Charlottesville and America," 17 Aug. 2017
Would not a Government so often revised become too mutable to retain those prejudices in its favor which antiquity inspires, and which are perhaps a salutary aid to the most rational Government in the most enlightened age?

— charles p. pierce, Esquire, "This Is the Bleakest Moment for America in My Lifetime," 13 Aug. 2017
This inability to engage with rational debate comes off as arrogance.

— tehrene firman, Allure, "9 Signs You Might Be Dating a Narcissist Right Now," 11 Aug. 2017
But rational people can also invest themselves, without even realizing it, in external sources of validation.

— carolyn hax, Detroit Free Press, "Children’s award ceremonies bring out mom’s jealousy," 9 Aug. 2017
No rational human being would choose the WET?C as their go-to in this hamburger bun-less scenario.

— alex delany, Bon Appetit, "What's the Correct Way to Eat a Hamburger on a Hot Dog Bun?," 4 Aug. 2017
Ignorance bred fear, and fear led to a coldly rational response: wholesale evacuation.

— richard campanella, NOLA.com, "New Orleans residents fled the city en masse every August in the 1800s but not for hurricanes," 1 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'rational.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of rational

Middle English racional, from Anglo-French racionel, from Latin rationalis, from ration-, ratio

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First Known Use: 14th century

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rational Synonyms

Synonyms

intelligent, reasonable, reasoning, thinking

rational

noun

Definition of rational

:something rational; specifically :rational number

First Known Use of rational

1601

RATIONAL Defined for English Language Learners

rational

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adjective

Definition of rational for English Language Learners

: based on facts or reason and not on emotions or feelings
: having the ability to reason or think about things clearly

RATIONAL Defined for Kids

rational

play

adjective ra·tio·nal \ ˈra-shə-nᵊl \

Definition of rational for Students

1 :having the ability to reason

Humans are rational creatures.

2 :based on or showing reason

rational thinking

a rational decision

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rationally

adverb

Medical Dictionary

rational

play

adjective ra·tio·nal \ ˈrash-nəl, -ən-ᵊl \

medical Definition of rational

1 a :having reason or understanding

b :relating to, based on, or agreeable to reason

a rational explanation

rational behavior

2 :using medical treatments based on reason or general principles —used especially of an ancient school of physicians — compare empirical 1a

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rationally

play \-ē\ adverb

Law Dictionary

rational

play

adjective ra·tio·nal \ ˈra-shə-nəl \

legal Definition of rational

1 :having reason or understanding

2 :relating to, based on, or guided by reason, principle, fairness, logic, a legitimate state interest, or a consideration of fact

age distinctions are not subject to strict scrutiny, but they must have a rational relationship to a legitimate state interest
—In re J. M., 642 A.2d 1062 (1994)

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rationality

play \ˌra-shə-ˈna-lə-tē\ noun

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rationally

adverb

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rational

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