A set is a collection of distinct objects. There are two ways to describe a set: roster form lists the elements between braces, and set-builder form uses a characteristic property P(x). Sets can be infinite, finite, empty, or singleton. Two sets are equal if they contain the same elements, and equivalent if they have the same number of elements. A set is a subset if all its elements are contained in another set, called the superset. Closed and open intervals are examples of subsets of real numbers. The power set is the collection of all subsets, and the universal set contains all sets in a given context. Venn diagrams use circles and rectangles to represent relationships between sets. Common set operations include union