English Reference
adjective · noun

rational

adj. · n.
US /ˈɹæʃənəɫ/ UK /ɹˈæʃənəl/ ra·tio·nal UK spelling rationals

  1. 01 B2 Upper Intermediate

    adj.based on clear thinking and facts rather than emotions.

    adj.based on or in accordance with reason or logic; exhibiting intellectual soundness.

    Simple

    We need to have a rational discussion about the budget instead of getting angry.

    In context

    The committee attempted to reach a rational conclusion by weighing the statistical evidence against the projected long-term costs.

  2. 02 C1 Advanced Academic

    adj.having the ability to think, understand, and use logic.

    adj.possessing the capacity for reason; often used to distinguish humans from other animals in philosophical contexts.

    Simple

    Aristotle famously described humans as rational animals.

    In context

    The debate centered on whether artificial intelligence could ever truly be considered a rational agent with its own intent.

  3. 03 B2 Upper Intermediate Technical Math

    adj.describing a number that can be shown as a simple fraction.

    adj.relating to or being a number that can be expressed as the quotient of two integers.

    Simple

    The number 0.75 is rational because it can be written as three-quarters.

    In context

    The proof demonstrates that while the square root of two is irrational, its square is a rational integer.

  4. 04 C1 Advanced Technical Math

    n.a number that can be expressed as one integer divided by another.

    n.a rational number; any value that can be represented as a ratio of two integers where the denominator is not zero.

    Simple

    In this equation, x must be a rational rather than an irrational number.

    In context

    The set of rationals is dense, meaning that between any two distinct rational numbers, there exists another rational.

Usage appreciation rational · rational approach · rational basis

This can be a more rational choice - fans might relate to the club's story, their culture and values, or simply like their kit.

BBC News· 15 Aug 2026

Schiller explains our sensuous and rational nature in terms of “drives”: the “sensuous drive,” rooted in feeling, and the “formal drive,” grounded in reason.

JSTOR Daily· 5 Aug 2026

Etymology 1

From Old French rationel, rational, from Latin rationalis (“of or belonging to reason, rational, reasonable; having a ratio”), from ratio (“reason; calculation”).

Etymology 2

From Old French rational, from Medieval Latin rationale (“a pontifical stole, a pallium, an ornament worn over the chasuble”), neuter of Latin rationalis (“rational”), for which see the first etymology. Translation of λογεῖον (logeîon) or perhaps λόγιον (lógion, “oracle”) in the Septuagint version of Exodus 28.

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

This entry
Origin Latin rationalis
Level C1 · Advanced
Frequency Common
Updated