"It's more like two-dimensional. Real numbers are like the x-axis on the complex plane, and imaginary numbers are like the y-axis. Another way to look at it is, each real number can be described as itself times the multiplicative unit, i.e. 5 is 5*sqrt(1), 24 is 24*sqrt(1), 1 is sqrt(1)2. That's their 'x unit'. Each imaginary number can be described as a number times the imaginary unit, sqrt(-1), or i. We'd say that the number 5i is imaginary and is equal to 5 times the imaginary unit. In geometric terms, it's 5 y-units on the complex plane. When you mix together imaginary and real numbers, you get a complex number, describing both its coordinates on the complex plane, except instead of (5, 10) for 5x and 10y, we have (5 + 10i) for 5*sqrt(1) and 10*sqrt(-1). I hope this is making some kind of sense. "