Rational a. : Relating to the reason; not physical; mental.

Rational a. : Having reason, or the faculty of reasoning; endowed with reason or understanding; reasoning.

Rational a. : Agreeable to reason; not absurd, preposterous, extravagant, foolish, fanciful, or the like; wise; judicious; as, rational conduct; a rational man.

Rational a. : Expressing the type, structure, relations, and reactions of a compound; graphic; -- said of formulae. See under Formula.

Rational n. : A rational being.

Example:
Whats the difference between irRational and Rational numbers?

Taxonomy
rational, ra, adjective, ly, adverb, rational number, ratio, tio, Dictionary, Synonyms, ræ, rash, Pronunciation, Mathematics, integers, English dictionary, rational explanation, rational origin.

Defination from the web:
Rational definition, agreeable to reason; reasonable; sensible: See more.