imaginary number

noun

Mathematics.

1. Also called imaginary, pure imaginary number. a complex number having its real part equal to zero.

imaginary number

noun

1. any complex number of the form i b , where i = √–1

imaginary number

1. A type of complex number in which the multiple of i (the square root of −1) is not equal to zero. Examples of imaginary numbers include 4 i and 2 − 3 i, but not 3 + 0 i (which is just 3).

2. See more at complex number

Word History and Origins

Origin of imaginary number¹

First recorded in 1905–10