higher-order function

In mathematics and computer science, a higher-order function (also functional, functional form or functor; not to be confused with the functor concept in category theory) is a function that does at least one of the following:

• takes one or more functions as arguments,
• returns a function as its result.

All other functions are first-order functions. In mathematics higher-order functions are also known as operators or functionals. The differential operator in calculus is a common example, since it maps a function to its derivative, also a function.