rational

adjective

1 a rational approach to the problem:

logical, reasoned, well reasoned, sensible, reasonable, cogent, coherent, intelligent, wise, judicious, sagacious, astute, shrewd, perceptive, enlightened, clear-eyed, clear-sighted, commonsensical, common-sense, well advised, well grounded, sound, sober, prudent, circumspect, politic;

down-to-earth, practical, pragmatic, matter-of-fact, hard-headed, with both one's feet on the ground, unidealistic;

informal joined-up.

▷antonyms irrational, illogical.

2 she was not fully rational at the time of signing the agreement:

lucid, coherent, sane, in one's right mind, able to think/reason clearly, of sound mind, in possession of all one's faculties;

normal, balanced, well balanced, clear-headed;

Latin compos mentis;

informal all there.

▷antonyms insane.

3 man is a self-conscious, rational being:

intelligent, thinking, discriminating, reasoning;

cognitive, mental, cerebral, logical, analytical, conceptual;

rare ratiocinative.

rational Oxford Dictionary of English