Definition:Empty Class (Class Theory)

Definition
A class is defined as being empty it has no elements.

That is:
 * $\forall x: x \notin A$

or:
 * $\neg \exists x: x \in A$

The empty class is usually denoted $\O$ or $\emptyset$. On the preferred symbol is $\O$.

Also see

 * Empty Class is Unique


 * Definition:Empty Set