English · Word Candidate

irrational

/ɪˈɹæʃ.(ə.)nəl/

Proposed by a contributor, not yet supported by evidence.

Also seen as: irrationals

Sense 1

Meaning · English

Not rational; unfounded, nonsensical or wrong-headed.

Adjective

Examples

an irrational decision

Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01)

Sources & notes

Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01 via kaikki.org).

Sense 2

Meaning · English

Of a real number, that cannot be written as the ratio of two integers.

Adjective

Examples

The number π is irrational.

Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01)

Sources & notes

Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01 via kaikki.org).

Sense 3

Meaning · English

A real number that can not be expressed as the quotient of two integers, an irrational number.

Noun

Examples

The square root of 2, which was the first irrational to be discovered, was known to the early Pythagoreans, and ingenious methods of approximating to its value were discovered.

Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01)

Sources & notes

Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01 via kaikki.org).

Common questions

What does “irrational” mean?

Not rational; unfounded, nonsensical or wrong-headed.

Is “irrational” formal or informal?

No register label has been reviewed yet — treat it as neutral and check the usage notes above.