# Definition:Singleton Class

## Definition

Let $a$ be a set.

The class $\set a$ is a singleton (class).

It can be referred to as singleton $a$.

## Also known as

Singleton $a$ can also be referred to as bracket $a$, but singleton $a$ is preferred, as it is less ambiguous.

## Examples

### Singleton Class of Empty Set

The singleton class $\O$ is the class whose only element is the empty set $\O$.

## Also see

• Results about singleton classes can be found here.