a. [ L. rationalis: cf. F. rationnel. See Ratio, Reason, and cf. Rationale. ] 1. Relating to the reason; not physical; mental. [ 1913 Webster ]

Moral philosophy was his chiefest end; for the rational, the natural, and mathematics . . . were but simple pastimes in comparison of the other. Sir T. North. [ 1913 Webster ]

2. Having reason, or the faculty of reasoning; endowed with reason or understanding; reasoning. [ 1913 Webster ]

It is our glory and happiness to have a rational nature. Law. [ 1913 Webster ]

3. Agreeable to reason; not absurd, preposterous, extravagant, foolish, fanciful, or the like; wise; judicious; as, rational conduct; a rational man. [ 1913 Webster ]

4. (Chem.) Expressing the type, structure, relations, and reactions of a compound; graphic; -- said of formulae. See under Formula. [ 1913 Webster ]

Rational horizon. (Astron.) See Horizon, 2 (b). --
Rational quantity (Alg.), one that can be expressed without the use of a radical sign, or in exact parts of unity; -- opposed to irrational or radical quantity. --
Rational symptom (Med.), one elicited by the statements of the patient himself and not as the result of a physical examination. [ 1913 Webster ]

Syn. -- Sane; sound; intelligent; reasonable; sensible; wise; discreet; judicious. -- Rational, reasonable. Rational has reference to reason as a faculty of the mind, and is opposed to irrational; as, a rational being, a rational state of mind, rational views, etc. In these cases the speculative reason is more particularly, referred to. Reasonable has reference to the exercise of this faculty for practical purposes, and means, governed or directed by reason; as, reasonable desires or plans; a reasonable charge; a reasonable prospect of success. [ 1913 Webster ]

What higher in her society thou find'st
Attractive, human, rational, love still. Milton. [ 1913 Webster ]

A law may be reasonable in itself, although a man does not allow it, or does not know the reason of the lawgivers. Swift. [ 1913 Webster ]

n. A rational being. Young. [ 1913 Webster ]

n. [ L. rationalis, neut. rationale. See Rational, a. ] An explanation or exposition of the principles of some opinion, action, hypothesis, phenomenon, or the like; also, the principles themselves. [ 1913 Webster ]

n. [ Cf. F. rationalisme. ] 1. (Theol.) The doctrine or system of those who deduce their religious opinions from reason or the understanding, as distinct from, or opposed to, revelation. [ 1913 Webster ]

2. (Philos.) The system that makes rational power the ultimate test of truth; -- opposed to sensualism, or sensationalism, and empiricism. Fleming. [ 1913 Webster ]

n. [ Cf. F. rationaliste. ] One who accepts rationalism as a theory or system; also, disparagingly, a false reasoner. See Citation under Reasonist. [ 1913 Webster ]

{ } a. Belonging to, or in accordance with, the principles of rationalism. -- Ra`tion*al*is"tic*al*ly, adv. [1913 Webster]

n.; pl. -ties [ F. rationalité, or L. rationalitas. ] The quality or state of being rational; agreement with reason; possession of reason; due exercise of reason; reasonableness. [ 1913 Webster ]

When God has made rationality the common portion of mankind, how came it to be thy inclosure? Gov. of Tongue. [ 1913 Webster ]

Well-directed intentions, whose rationalities will never bear a rigid examination. Sir T. Browne. [ 1913 Webster ]

n. The act or process of rationalizing. [ 1913 Webster ]

v. i. To use, and rely on, reason in forming a theory, belief, etc., especially in matters of religion: to accord with the principles of rationalism. [ 1913 Webster ]

Theodore . . . is justly considered the chief rationalizing doctor of antiquity. J. H. Newman. [ 1913 Webster ]

v. t. 1. To make rational; also, to convert to rationalism. [ 1913 Webster ]

2. To interpret in the manner of a rationalist. [ 1913 Webster ]

3. To form a rational conception of. [ 1913 Webster ]

4. (Alg.) To render rational; to free from radical signs or quantities. [ 1913 Webster ]