An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A → real number which cannot be exactly expressed as a ratio ^a/_b of two integers. Irrational numbers have decimal expansions that neither terminate nor become periodic. Every → transcendental number is irrational. The most famous irrational number is √ 2.

From ir- a prefix meaning "not," a variant of → in-, + → rational; → number.