Mathematicians and scientists use orders of magnitude, also called orders of ten, to describe how big a number is. The zero order of magnitude means exactly one. One order of magnitude means about 101, or 10. Two orders of magnitude means about 102 or 100. In order to help you visualize orders of magnitude, each of the following chapters has as many dots as the order. For example, for order of magnitude 3, there are 1,000 dots. For order of magnitude 4 there are 10,000 dots.