Is every real number a complex number?

A complex number is a number of the form a + bi, where a and b are real numbers and i is the principal square root of -1. In the special case where b=0, a+0i=a. Hence every real number is also a complex number. And in the special case where a=0, we call those numbers pure imaginary numbers.

Note that 0=0+0i, therefore 0 is both a real number and a pure imaginary number.

Do not confuse the complex numbers with the pure imaginary numbers.

Every real number is a complex number and every pure imaginary number is a complex number also.