rational |ˈra sh ənl; ˈra sh nəl|
1 based on or in accordance with reason or logic : I'm sure there's a perfectly rational explanation.
• (of a person) able to think clearly, sensibly, and logically : Andrea's upset—she's not being very rational.
See note at sensible .
• endowed with the capacity to reason : man is a rational being.
2 Mathematics (of a number, quantity, or expression) expressible, or containing quantities that are expressible, as a ratio of whole numbers. When expressed as a decimal, a rational number has a finite or recurring expansion.
a rational number.
rationality |ˌra sh əˈnalətē| noun
rationally |ˈra sh ənl-ē; ˈra sh nəlē| adverb
ORIGIN late Middle English (in the sense [having the ability to reason] ): from Latin rationalis, from ratio(n-) ‘reckoning, reason’ (see ratio ).