I. ˈrashən ə l, -shnəl, ˈraash-, ˈraish- adjective
Etymology: Middle English racional, from Latin rationalis, from ration-, ratio reason, computation, reasoning + -alis -al
1. : having reason or understanding : reasoning
rational creature
a rational being
embryo had a vegetable life, then an animal life, and finally a rational life — S.F.Mason
2.
a. : of, relating to, or based upon reason
provide a literary as well as a rational education — G.K.Chalmers
rational analysis of the problem — R.C.Doty
b. : using medical treatments based on reason or general principles — used especially of an ancient school of physicians; opposed to empirical
3. : involving only multiplication, division, addition, and subtraction and only a finite number of times : not involving a surd or indicated but not extractable root
3 and 2 + 3/5 are rational expressions
4.
a. : agreeable to reason : intelligent , sensible
gives a quite rational explanation of the passage — Modern Language Notes
a rational … world trade policy — Nation's Business
the advantages of a rational orthography — C.H.Grandgent
b. : rationalistic
5. : capable of being measured in terms of the mora in Greek and Latin prosody : having the normal ratio between arsis and thesis
Synonyms:
reasonable: rational usually implies a latent or active power to make logical inferences and draw conclusions that enable one to understand the world about him and relate such knowledge to the attainment of ends, often, in this use, opposed to emotional or animal; in application to policies, projects, or acts, rational implies satisfactory to the reason or chiefly actuated by reason
the triumph of the rational over the emotional side of man
his was a mind so purely rational that it had long since demanded and received absolute divorce from his naturally impetuous heart — Elinor Wylie
the rational, the intelligent, the orderly processes of behavior — Lewis Mumford
we may seek to change another person's convictions in a rational manner either by bringing to his notice evidence that he did not previously know about or by inducing in him a process of rational inference — R.H.Thouless
reasonable usually carries a much weaker implication of the power to reason in general or of guidance by conclusions drawn by the reasoning power, rather applying to actions or decisions or choices that are practical, sensible, just, or fair
the longing to achieve is more emotional than reasonable — H.S.Canby
no English author has given an ampler and more reasonable interpretation of life — W.S.Maugham
the amount of uncompleted work is relatively small and can be completed within a reasonable period of time — Loyola University Bulletin
the heifers and cows may be expected to give a reasonable milk yield — Allan Fraser
contributions must be reasonable in amount — C.M.Winslow
II. noun
( -s )
: something rational: as
a. archaic : a rational creature ; especially : a human being
not as rationals, but as animals — Thomas Paine
b. : a rational expression in mathematics
consider the set of all rationals, excluding zero — Harry Lass
c. : rationale
the decided shift in production rational — Dun's Review
III. adjective
: relating to, consisting of, or being one or more rational numbers