agreeable to reason; reasonable; sensible

a rational plan for economic development.

having or exercising reason, sound judgment, or good sense

a calm and rational negotiator.

being in or characterized by full possession of one's reason; sane; lucid

The patient appeared perfectly rational.

endowed with the faculty of reason

rational beings.

of, pertaining to, or constituting reasoning powers

the rational faculty.

proceeding or derived from reason or based on reasoning

a rational explanation.

Mathematics .

capable of being expressed exactly by a ratio of two integers.

(of a function) capable of being expressed exactly by a ratio of two polynomials.

Classical Prosody . capable of measurement in terms of the metrical unit or mora.

Mathematics . rational number.

noun

logic , rationale , rationality , reason