Complement (set)

All elements (from a universal set) not in our set.

Example: With a universal set of {1,2,3,4,5,6}
the complement of {5,6} is {1,2,3,4}

The symbol is a little dash in the top-right corner.
Example: A' = {1,2,3,4}

Or a little "C" in the top-right corner.
Example: A^C = {1,2,3,4}

Together the set and its complement make the universal set.

Another Example, for the set below:
• the universal set is {alex, blair, casey, drew, erin, francis, glen, hunter, ira, jade}
• set S = {alex, casey, drew, hunter}
• the complement of set S is: S^C = {blair, erin, francis, glen, ira, jade}