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
: something rational
specifically
: rational number
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
Jens Ludwig, Time, 15 May 2025
The ban on water fluoridation by the Florida Legislature (SB 700) and the outspoken views of the state surgeon general are the antithesis of rational public health measures.
—Sun Sentinel Editorial Board, Sun Sentinel, 4 May 2025
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
See All Example Sentences for rational
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Adjective
What’s more, behavioral economics suggests that our deviations from rational, deliberate behavior has some predictable structure.
—Jens Ludwig, Time, 15 May 2025
The ban on water fluoridation by the Florida Legislature (SB 700) and the outspoken views of the state surgeon general are the antithesis of rational public health measures.
—Sun Sentinel Editorial Board, Sun Sentinel, 4 May 2025
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
See All Example Sentences for rational
Cite this Entry
“Rational.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rational. Accessed 29 May. 2025.
Copy CitationKids 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
adverb
-ē
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
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)
In re J. M., 642 A.2d 1062 (1994)
rationally
adverb
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