In mathematics an theoretical computer science, the broadest and most abstract definition of an enumeration of a set is an exact listing of all of its elements (perhaps with repetition). The restrictions imposed on the type of list used depend on the branch of mathematics and the context in which one is working. In more specific settings, this notion of enumeration encompasses the two different types of listing: one where there is a natural ordering and one where the ordering is more nebulous. These two different kinds of enumerations correspond to a procedure for listing all members of the set in some definite sequence, or a count of objects of a specified kind, respectively. While the two kinds of enumeration often overlap in most natural situations, they can assume very different meanings in certain contexts.