although the notation is identical for cardinality of a set and the absolute value of a real number, we should have no trouble distinguishing between the two. A set S is finite if ISI nonnegative integer n. A set S is infinite if it is not finite. For the present, we will use the notation ISI only for finite sets S. In Chapter 10, we will discuss the cardinality of infinite sets. Let's now consider a few examples of sets that are defined in terms of the special sets we have just described.