In mathematics, a unary function is a function that takes one argument. A unary operation is a special kind of unary function, whose codomain coincides with its domain.

The successor function is a unary function. More specifically, it is a unary operation on the set of natural numbers.

Many of the elementary functions are unary functions, including the trigonometric functions, logarithm with a specified base, exponentiation to a particular power or base, and hyperbolic functions.

• Arity
• Binary function
• Binary operation
• Iterated binary operation
• Ternary operation
• Unary operation

• Foundations of Genetic Programming