| Noun | 1. | complex quantity - (mathematics) a number of the form a+bi where a and b are real numbers and i is the square root of -1 math, mathematics, maths - a science (or group of related sciences) dealing with the logic of quantity and shape and arrangement number - a concept of quantity involving zero and units; "every number has a unique position in the sequence" complex conjugate - either of two complex numbers whose real parts are identical and whose imaginary parts differ only in sign real, real number - any rational or irrational number pure imaginary number - an imaginary number of the form a+bi where a is 0 imaginary part, imaginary part of a complex number - the part of a complex number that has the square root of -1 as a factor |