English Reference
noun

rationality

n.
US /ˌɹæʃəˈnæɫɪti/ UK /ɹˌæʃənˈælɪti/ ra·tio·nal·i·ty UK spelling rationalities

  1. 01 C1 Advanced Academic

    the ability to think clearly and make decisions based on reason and facts.

    the quality of being consistent with or based on logic and reason. Uncountable in its general sense.

    Simple

    We need to use rationality rather than anger to solve this problem.

    In context

    The philosopher argued that human rationality is often compromised by deep-seated cognitive biases and emotional responses.

    Usage

    Often used with the definite article 'the' or as an abstract uncountable noun.

    irrationalityillogic
  2. 02 C2 Proficiency AcademicFormal

    a particular way of thinking or a set of reasons for doing something.

    a specific rational motive or a system of beliefs based on logical principles. Countable in this specific context.

    Simple

    The economic rationality behind the decision was difficult for the public to understand.

    In context

    The study examines the competing rationalities of environmental activists and industrial developers during the planning phase.

    Usage

    Can be used in the plural ('rationalities') when comparing different systems of thought.

Mission Control embodied everything I loved about humanity and learning: teamwork, creativity, rationality, calmness and respect for the data and the facts.

The Guardian· 22 Aug 2026

They also included approaches based on the principle of bounded rationality, which are designed to facilitate decision-making by highlighting specific aspects of climate change, such as its health or financial consequences.

Phys.org· 1 Sept 2026

From rational + -ity, from French rationalité, from Late Latin rationalitas (“rationality, reasonableness”), from Latin rationalis (“reasonable”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level C1 · Advanced
Frequency Occasional
Updated