In mathematics, a set is a collection of distinct objects. Each object, or element, can occur at most once. Ordering is not significant: sets do not impose any ordering on their elements.

Sets are usually named using capital letters, and brackets, {}, are used to enumerate a set’s elements. For example:

Two sets are considered equal if and only if they contain exactly the same elements.

**Symbols:**

denotes set membership. i.e., . We can say that is a member of or belongs to . We can also say that contains .

means that an element is not a member of a set.

Sets may be finite or infinite. is an example of an infinite set.

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