- noun a complex number written as a + ib, where i is the square root of minus one, and b is not equal to zero
- A number in the form of bi, in which b is a real number, and i is the square root of -1. That is, i2 = -1. In electronics, the symbol utilized to express the square root of -1 is usually j. A complex number has the form of a + bi, in which a and b are real numbers, and i is the square root of -1. Also called imaginary quantity.
- synonymimaginary quantity