A term describing a set which is isomorphic to a subet of the natural numbers. A countable set has "countably many" elements. If the isomorphism is stated explicitly then the set is called "a counted set" or "an enumeration". Examples of countable sets are any finite set, the {natural numbers}, {integers}, and {rational numbers}. The {real numbers} and {complex numbers} are not [proof?]. (1999-08-29)
