Unary operation
（重定向自Monadic operator）
In mathematics, a unary operation is an operation with only one operand, i.e. a single input. An example is the function f : A → A, where A is a set. The function f is a unary operation on A.
Common notations are prefix notation (e.g. +, −, not), postfix notation (e.g. factorial n!), functional notation (e.g. sin x or sin(x)), and superscripts (e.g. transpose A). Other notations exist as well. For example, in the case of the square root, a horizontal bar extending the square root sign over the argument can indicate the extent of the argument.