The relative complement of two sets and $B$ , denoted $A ∖ B$ , is the set of elements that are in $A$ while not in $B$ .

illustration of the output of a relative complement

Formally stated, where $C = A ∖ B$

$x \in C \leftrightarrow (x \in A \land x \notin B)$

That is, Iff $x$ is in the relative complement $C$ , then $x$ is in $A$ and x is not in $B$ .

For example,

If we name the set $U$ as the set of all things, then we can define the Absolute complement of the set $A$ , $A^{∁}$ , as $U ∖ A$