Finite Set - Definition and Terminology

Definition and Terminology

Formally, a set S is called finite if there exists a bijection

for some natural number n. The number n is called the cardinality of the set, and is denoted |S|. (Note that the empty set is considered finite, with cardinality zero.) If a set is finite, its elements may be written as a sequence:

In combinatorics, a finite set with n elements is sometimes called an n-set and a subset with k elements is called a k-subset. For example, the set {5,6,7} is a 3-set, a finite set with three elements, and {6,7} is a 2-subset of it.