Imaginary number
One way of thinking about imaginary numbers is to say that they are to negative numbers what negative numbers are to positive numbers. If we say "go east by -1 mile", it is the same as if we had said "go west by 1 mile". If we say "go east by i miles", it means the same thing as if we had said "go north by 1 mile". Similarly, if we say "go east by -i mile", it means the same as if we had said "go south by 1 mile".