(noun, adjective)


1. not consistent with or using reason

- irrational fears

- irrational animals

Similar word(s): incoherent, illogical, unlogical, blind, unreasoning, reasonless, nonrational, superstitious, unreasonable

2. (in mathematics) Of a real number, that cannot be written as the ratio of two integers.

- irrational numbers

Sentences with irrational as an adjective:

- an irrational decision

- The number π is irrational.


1. a real number that cannot be expressed as a rational number

Definition categories: quantity, real