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

(mathematical analysis) A function whose codomain is a topological space and domain is a measurable space, with the property that the inverse image of every open set in its codomain is a measurable set in its domain.

(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) 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.

(logic) An expression containing algebraic symbols that serve to represent words or other elements of a sentence or proposition

(mathematics) A function of a complex variable obtained by differentiating the logarithm of a gamma function; the digamma function / (physics) The Schrödinger wave function

(mathematics) A generalization of the indicator function for a fuzzy set which assigns a truth value (0 or 1) to each element.

(mathematics) a meromorphic function

(statistics) Any function used to obtain a set of samples from a given population

(mathematics) Any function, of multiple variables, whose value is independent of the order of the variables, i.e. f(a,b) = f(b,a).