imaginary number

noun Mathematics.

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

noun

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

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 4i and 2 – 3i, but not 3 + 0i (which is just 3). See more at complex number.