countable set A set that is either finite or countably infinite. A countably infinite set is one that can be put in one-to-one correspondence with the natural numbers and thus has a cardinal number ("size") of aleph-null. Examples of countable sets include the set of all people on Earth and the set of all fractions. Related entry infinity Related category MATHEMATICS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |