Definition:Class Difference

Definition
Let $A$ and $B$ be two classes.

The (class) difference $A \setminus B$ of $A$ and $B$ is defined as the class of all sets $x$ such that $x \in A$ and $x \notin B$:


 * $x \in A \setminus B \iff x \in A \land x \notin B$

or:
 * $A \setminus B = \set {x: x \in A \land x \notin B}$

Also see

 * Definition:Set Difference, the usual presentation of this concept in set theory