What term describes a nonzero number that is a real multiple of the imaginary unit i?

Imaginary number

Imaginary numbers are defined as the product of a real number and the imaginary unit i, which represents the square root of -1. While the name suggests they aren't "real," they are essential in electrical engineering and physics for modeling complex wave patterns. A memorable way to identify them is that squaring any purely imaginary number will always result in a negative real number.