Numbers fall into several broad categories: natural numbers, integers, rational numbers, irrational numbers, and even complex numbers. How many of these categories are you familiar with? Why is it important to have categories of numbers and to know which categories you are dealing with in a given expression? One category that is important to understand is rational numbers. A rational number is a number that can be expressed as an integer divided by another integer. In this unit you will encounter rational expressions, which are a form of polynomial. Knowing what the definition of rational numbers is, what form do you expect rational expressions to take?