In trinary algebra, which involves three-level logic with states that can be represented by the numbers -1, 0, and 1, there are five unary operators. They are called invert, rotate-up, rotate-down, shift-up, and shift-down. The actions performed by these operators are denoted in the following table.
In common arithmetic, the unary operators are negation, the reciprocal, and the absolute value. Negation involves reversing the sign of a number. For example, the negation of 4 is -4, and the negation of -23 is 23. The reciprocal involves dividing 1 by the number. Thus, the reciprocal of 4 is 1/4, and the reciprocal of -23 is -1/23. The absolute value involves reversing the sign of a number if it is negative, and leaving the number unchanged if it is 0 or positive. Thus, the absolute value of 4 is 4, and the absolute value of -23 is 23.
In set theory, there is one unary operator, called complementation. Given a set S that is a subset of some universal set U , the complement of S , written S' , is the set containing all elements of U that are not in S .