pertaining to rationality

the most central paradigm of Rational-Emotive Therapy

a mathematical term for certain numbers; the rational numbers

Rational, one of the four temperaments according to the Keirsey Temperament Sorter.

the software company Rational Software; now owned by IBM, and formerly Rational Software Corporation

A rational function, a mathematical function which can be written as the ratio of two polynomial functions.

acting according to the philosophical principles of rationalism