In
set theory, the symmetric
difference of two
sets A and B is the set of elements which appear in exactly one of A or B. In other words, it is the
union of A and B
minus their
intersection. This operator is both
commutative and
associative. It is usually represented by an uppercase
delta.
For example, consider the set of positive even numbers, and the set of positive multiples of 3. The symmetric difference of these two sets is the set {2, 3, 4, 8, 9, 10, 14, 15, 16, ...}