Difference of two sets

An operation on sets. Let $A$ and $B$ be two sets (where the second need not be contained in the first). Then the set of those elements of $A$ that are not elements of $B$ is called the difference of these sets.

The difference between two sets $A$ and $B$ is denoted by $A\setminus B$.

Comments

When $B$ is a subset of $A$, the difference is often termed the complement or relative complement of $B$ in $A$.

See also Symmetric difference of sets.

References

[a1]	P. R. Halmos, Naive Set Theory, Springer (1960) ISBN 0-387-90092-6