rationality

UK: /ˌræʃəˈnælɪtɪ/ US: /ˌræʃəˈnælɪti/ ,(rash′ə nal′i tē)

Inflections of 'rationality' (n): npl: rationalities

WordReference Random House Unabridged Dictionary of American English © 2025

ra•tion•al•i•ty  (rash′ə nal′i tē), n., pl. -ties. 

1. the state or quality of being rational.
2. the possession of reason.
3. agreeableness to reason;
   reasonableness.
4. the exercise of reason.
5. a reasonable view, practice, etc.

• Late Latin ratiōnālitās reasonableness. See rational, -ity
• 1560–70

Collins Concise English Dictionary © HarperCollins Publishers::

rationality / ˌræʃəˈnælɪtɪ/ noun ( -ties)

1. the state or quality of being rational or logical
2. the possession or utilization of reason or logic
3. a reasonable or logical opinion
4. the assumption that an individual will compare all possible combinations of goods and their prices when making purchases

WordReference Random House Learner's Dictionary of American English © 2025

ra•tion•al /ˈræʃənəl, ˈræʃnəl/   adj. 

1. based on reason; fitting in with reason;
   sensible:
   a rational decision.
2. using reason:
   a rational negotiator.
3. sane;
   able to think or speak clearly and logically:
   The patient seems perfectly rational.

ra•tion•al•i•ty /ˌræʃəˈnælɪti/  n. [uncountable]
ra•tion•al•ly, adv. See -ratio-.

WordReference Random House Unabridged Dictionary of American English © 2025

ra•tion•al  (rash′ə nl, rash′nl), adj. 

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.
3. being in or characterized by full possession of one's reason;
   sane;
   lucid:
   The patient appeared perfectly rational.
4. endowed with the faculty of reason:
   rational beings.
5. of, pertaining to, or constituting reasoning powers:
   the rational faculty.
6. proceeding or derived from reason or based on reasoning:
   a rational explanation.
7. Mathematics
   • capable of being expressed exactly by a ratio of two integers.
   • (of a function) capable of being expressed exactly by a ratio of two polynomials.
8. Poetry [Class. Pros.] capable of measurement in terms of the metrical unit or mora.

n. 

9. [Math.] See rational number. 

• Latin ratiōnālis, equivalent. to ratiōn- (stem of ratiō) reason + -ālis -al¹
• Middle English racional 1350–1400

ra′tion•al•ly, adv. 
ra′tion•al•ness, n. 
Synonyms

• 2. intelligent, wise, judicious, sagacious, enlightened.
• 6. See reasonable. 

Antonyms

• 2. stupid.
• 3. insane.