rational >> /ˈræʃ(ə)n(ə)l/
Definition: [noun] A rational number.
Example: The construction of the reals from the integers proceeds in several stages: first axiomatize the positive integers, then construct negative from positive integers, then rationals from integers, and finally reals from rationals.
Definition: [adjective] Based on or in accordance with reason or logic.
Example: I'm sure there's a perfectly rational explanation
Definition: [adjective] (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.
Example: The set of rational numbers is denumerable, that is, it has cardinal number d.