This is a complex number.
It has a real part (2) and an imaginary part (4).
A complex number is of the form [tex]a+bi[/tex], where a is the real part, and b is the imaginary part.
In reality, there's no such thing as a pure imaginary number; rather, it is a complex number with a real part equal to 0, but use the naming conventions your instructor recommends.
