(mathematics) In harmonic analysis, any of a complete orthogonal set of functions that can be used to represent any discrete function.

(combinatorics) A Boolean function f: Z ₂ⁿ→ Z ₂ whose Walsh transform has constant absolute value.

(mathematics) A function obtained from a continuous function by transfinite iteration of the operation of forming pointwise limits of sequences of functions.

plural of functional root

(physics) A function, denoted by Ai(x), that is a solution to the Airy equation.

(programming) A function that belongs to a class and can be called on instances of the object defined by that class.

(mathematics) The function that determines the sign of a real number, yielding -1 if negative, +1 if positive, or otherwise zero.

(mathematics) A function whose range is a subset of the set of real numbers.

(mathematics) A function whose range is a subset of the set of complex numbers.

(mathematical analysis) A function which is equal to 1 for all points in its domain which belong to a given set, and is equal to 0 for all points in the domain which do not belong to that given set.