Definition:Unordered Tuple

Definition
An unordered tuple is a small class in Zermelo-Fraenkel set theory that contains a finite number of elements.

It is written using roster notation and is denoted:
 * $\set {a_1, a_2, \ldots, a_n}$

that is:
 * $\set {a_1, a_2, \ldots, a_n} = \set {x: x = a_1 \lor x = a_2 \lor \dots \lor x = a_n}$