Definition:Singleton Class

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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.


Singleton Class of Empty Set

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

Also see

  • Results about singleton classes can be found here.