Synonyms for Rational:

adj.

calculational (adjective)
calculational, approximate, mathematical, numerical, Systematical, statistical, methodical, geometric, algorithmic, computational, proportional, judgmental, algebraic, suppositional, arithmetic, valuational.
calm (adjective)
level-headed.
commonsensical (adjective)
commonsensible.
intellectual (adjective)
thinking, brainy, cerebral, egghead, intelligent, psychological, understanding, intellectual, reasoning.
levelheaded (adjective)
levelheaded.
ratiocinative (adjective)
ratiocinative.
realistic; of sound mind (adjective)
intelligent, reasoning, cool, lucid, intellectual, deliberate, normal, sober, enlightened, wise, ratiocinative, deductive, analytical, thinking, circumspect, prudent, reflective, sensible, knowing, synthetic, impartial, sound, objective, philosophic, levelheaded, discriminating, calm, collected, reasonable, cerebral, balanced, sane, logical, stable, thoughtful, together.
reasonable (adjective)
sensible, thought-out, inductive, deductive, plausible, wise, sound, likely, feasible, intelligent, cogent, conceivable, reasonable, thinking, logical.
sane (adjective)
down-to-earth, Sober-minded, sensible, realistic, clearheaded, sane, responsible, lucid, normal, balanced, well-balanced, reasonable.
sober (adjective)
Clear-headed.
sound (adjective)
well-founded.

adv

a priori (adverb)
deductive.

n.

analytic, reason. well-founded, levelheaded, commonsensible, well-grounded, sapient, commonsensical. Compos-mentis. consequent. rational (noun)
sane, noetic, mental, lucid, reasoning, demythologized, thinking, intelligent, logical, demythologised, coherent, reasonable, intellectual.

Other synonyms:

Clear-headed, analytic, collected, discriminating, levelheaded, ratiocinative, pragmatic, commonsensical, commonsensible, analytical, Compos-mentis, enlightened, thoughtful, well-grounded. well-founded, reason, consequent, responsible. prudent, sapient. mature. matter of fact
practical.
wise
level-headed.

Usage examples for rational

  1. My love is the most rational thing of my life." – From Jest to Earnest by E. P. Roe
  2. Now Carlsruhe was in those days one of the dullest places rational man ever condescended to inhabit. – Fragments of an Autobiography by Felix Moscheles
  3. The conclusion which I wish to draw is obvious: make women rational creatures and free citizens, and they will quickly become good wives and mothers; that is, if men do not neglect the duties of husbands and fathers. – Mary Wollstonecraft by Elizabeth Robins Pennell