Minus

operand1 - operand2

If operand1 and operand2 both result in numbers, the expression results in operand1 minus operand2. If both operands result in sets, the expression results in the set of all members of operand1 which are not also members of operand2. Otherwise it results in Undefined.

For example:

  5 - 3 = 2
  3 - 5 = -2
  {1, 2, 3} - {2} = {1, 3}
  {2} - {1, 2, 3} = {}
  {1} - {2} = {1}