Symmetric difference: The symmetric difference of set A and set B is defined as the set of all elements in set A and set B that do not belong to A∩B, denoted by A△B, that is, A△B={x|x∈A∪B,x∉A∩B}, that is, A△B=(A∪B)-(A∩B). That is, A△B=（A-B）∪（B-A）

Obviously, the symmetric difference operation satisfies the commutative law: A△B=B△A. The symmetric difference operation is also called symmetric difference.