rational

1 of 2

adjective

ra·​tio·​nal ˈrash-nəl 

ˈra-shə-nᵊl

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

rationally adverb

rationalness noun

rational

2 of 2

noun

: something rational

specifically : rational number

Synonyms

Adjective

• intelligent
• reasonable
• reasoning
• thinking

Examples of rational in a Sentence

Adjective

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 on the Web

Adjective

But the curve also has a second family of rational points. —Joseph Howlett, Quanta Magazine, 11 Nov. 2024

It can also be made more orderly, rational, and humane. —Eladio B. Bobadilla / Made By History, TIME, 5 Nov. 2024

Noun

For instance, in one group, collect all rationals that, when squared, are less than 2; in the other, put all rationals whose squares are greater than 2. —Jordana Cepelewicz, Quanta Magazine, 21 June 2024

At the time the database had a little over 3 million elliptic curves over the rationals. —Lyndie Chiou, Quanta Magazine, 5 Mar. 2024

Word History

Etymology

Adjective

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

First Known Use

Adjective

14th century, in the meaning defined at sense 1a

Noun

1601, in the meaning defined above

Phrases Containing rational

• anti-rational
• hyper-rational
• rational function
• rational number
• sub-rational

Kids Definition

rational

1 of 2 adjective

ra·​tio·​nal ˈrash-nəl 

-ən-ᵊl

1

a

: having the ability to reason

rational beings

b

: relating to, based on, or showing reason : reasonable sense 2

rational behavior

2

: relating to or involving rational numbers

a rational fraction

rationally

-ē

adverb

rational

2 of 2 noun

: something rational

especially : rational number

Medical Definition

rational

adjective

ra·​tio·​nal ˈrash-nəl, -ən-ᵊl 

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 sense 1a

rationally

-ē 

adverb

Legal Definition

rational

adjective

ra·​tio·​nal ˈra-shə-nəl 

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)

rationality

ˌra-shə-ˈna-lə-tē 

noun

rationally adverb