rational

¹ra·tio·nal

adjective \ˈrash-nəl, ˈra-shə-n^əl\

Definition of RATIONAL

1

a : having reason or understanding

b : relating to, based on, or agreeable to reason : reasonable <a rational explanation> <rational behavior>

2

: involving only multiplication, division, addition, and subtraction and only a finite number of times

3

: relating to, consisting of, or being one or more rational numbers <a rational root of an equation>

— ra·tio·nal·ly adverb

— ra·tio·nal·ness noun

Examples of RATIONAL

1. <human beings are rational creatures>
2. <insisted there was a rational explanation for the strange creaking noises and that there were no such things as ghosts>

Origin of RATIONAL

Middle English racional, from Anglo-French racionel, from Latin rationalis, from ration-, ratio

First Known Use: 14th century

Related to RATIONAL

Synonyms

intelligent, reasonable, reasoning, thinking

Antonyms

irrational, nonrational, nonthinking, unintelligent, unreasonable, unreasoning, unthinking

Related Words

analytic (or analytical), logical; brainy, cerebral, highbrow, highbrowed, intellectual; cognitional, cognitive, mental; levelheaded, practical, sane, sensible, sober

Near Antonyms

brainless, dense, doltish, dopey (also dopy), dorky [slang], dull, dumb, fatuous, half-witted, mindless, obtuse, senseless, slow, stupid, thickheaded; fallacious, groundless, illogical, invalid, nonsensical

Rhymes with RATIONAL

national, passional

²rational

noun

Definition of RATIONAL

: something rational; specifically : rational number

First Known Use of RATIONAL

1606

ra·tio·nal

adjective \ˈrash-nəl, -ən-^əl\   (Medical Dictionary)

Medical Definition of RATIONAL

1

a : having reason or understanding b : relating to, based on, or agreeable to reason <a rational explanation> <rational behavior>

2

: using medical treatments based on reason or general principles—used especially of an ancient school of physicians; compare empirical 1a

—ra·tio·nal·ly \-ē\ (audio pronunciation) adverb