(computing) Any of a set of subroutines that perform standard mathematical functions included in a programming language; either included in a program at compilation time, or called when a program is executed

(mathematics) A function where the independent variable is raised to a particular real number power.

(mathematics) Any function whose value repeats after the regular addition of a period to its independent variable; i.e., a function ƒ such that, for some positive constant p, ƒ(x + p) = ƒ(x) for all x.

(mathematics) Any function that applies constraints to a maximum or minimum problem

(mathematics) Either of a pair of functions whose inner product is zero

(mathematics) A function whose domain is a subset of the set on which it is formally defined; i.e., a function f: X→Y for which values f(x) are defined only for x ∈ W, where W ⊆ X.

(mathematics) An orthogonal function whose inner product with itself is unity

(mathematics) Any function whose value changes sign if the independent variable changes sign i.e. f(-x) = -f(x)

(mathematics) Any function whose value is the solution of a polynomial; an element of a subring of the ring of all functions over an integral domain, which subring is the smallest to contain all the constant functions and also the identity function. (If the polynomial is multivariate then there is a different identity function corresponding to each variable.)

(astronomy) A function that describes the angular distribution of light reflected from a body when illuminated from a specific direction