A denumerable (or countable) set is one for which there is a correspondence from the set to N, the set of natural numbers. To put it in another way: the cardinality of the set is equal to that of the natural numbers. Every infinite subset S of the...

A set, which should be thought of simply as a collection of objects, is called countable if it either consists of a finite number of objects or if the objects can be put in one to one correspondence with the integers. Two sets are defined to be of the...

In mathematics, a countable set is a set with the same cardinality (i.e., number of elements) as some subset of the set of natural numbers. The term was originated by Georg Cantor; it stems from the fact that the natural numbers are often called...