rational

[ rash-uh-nl, rash-nl ]

adjective

1. agreeable to reason; reasonable; sensible:

   a rational plan for economic development.

2. having or exercising reason, sound judgment, or good sense:

   a calm and rational negotiator.

   Synonyms: sagacious, judicious, wise, intelligent

   Antonyms: stupid

3. being in or characterized by full possession of one's reason; sane; lucid:

   The patient appeared perfectly rational.

   Antonyms: insane

4. endowed with the faculty of reason:

   rational beings.

5. of, relating to, or constituting reasoning powers:

   the rational faculty.

6. proceeding or derived from reason or based on reasoning:

   a rational explanation.

7. Mathematics.
   1. capable of being expressed exactly by a ratio of two integers.
   2. (of a function) capable of being expressed exactly by a ratio of two polynomials.
8. Classical Prosody. capable of measurement in terms of the metrical unit or mora.

noun

1. Mathematics. rational number.

rational

/ ˈræʃənəl /

adjective

1. using reason or logic in thinking out a problem
2. in accordance with the principles of logic or reason; reasonable
3. of sound mind; sane

   the patient seemed quite rational

4. endowed with the capacity to reason; capable of logical thought

   man is a rational being

5. maths expressible as a ratio of two integers or polynomials

   a rational number; a rational function

noun

1. maths a rational number

Derived Forms

• ˈrationally, adverb
• ˈrationalness, noun

Other Words From

• ra·tion·al·ly adverb
• ra·tion·al·ness noun
• an·ti·ra·tion·al adjective
• hy·per·ra·tion·al adjective
• non·ra·tion·al adjective
• o·ver·ra·tion·al adjective
• pre·ra·tion·al adjective
• qua·si-ra·tion·al adjective
• trans·ra·tion·al adjective
• ul·tra·ra·tion·al adjective
• un·ra·tion·al adjective

Word History and Origins

Origin of rational¹

First recorded in 1350–1400; Middle English racional, from Latin ratiōnālis, equivalent to ratiōn- (stem of ratiō ) reason + -ālis -al ¹

Word History and Origins

Origin of rational¹

C14: from Latin ratiōnālis , from ratiō reason

Synonym Study

See reasonable.

Example Sentences

"We relied on rational design, not trial and error, to make the catalyst better," Polo-Garzon added.

From Science Daily

In a rational world, this idea would have been consigned to the dumpster long ago, and forever.

From Los Angeles Times

Younger people are taking a more rational and nuanced review of all energy, and they’re coming to the same conclusion: Yeah, nuclear checks all the boxes,” Pittman said.

From Los Angeles Times

If I need to have ‘hope’ to motivate me, what will I do when I see no rational reason for hope?

From Salon

In too many ways, they appear locked in an echo chamber, largely talking to each other and convincing themselves that all intelligent and rational people agree with them.

From Salon

Related Words

• analytical
• balanced
• deliberate
• enlightened
• impartial
• intelligent
• judicious
• levelheaded
• logical
• lucid
• normal
• prudent
• reasonable
• sane
• sensible
• sober
• stable
• thoughtful
• wise