(mathematics) a meromorphic function

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

(chemistry) The relationship between the acidity of a solution and the concentration of its solute.

(mathematics) Any function in which an independent variable is in the form of an exponent; they are the inverse functions of logarithms

(mathematics) Any function of a complex variable which is periodic in two directions.

(mathematical analysis, algebraic geometry) A function defined by a (multivariable) implicit equation when one of the variables is regarded as the value of the function, especially where said equation is such that the value is not directly calculable from the other variables.

(mathematics) For a given function f, another function, denoted f⁻¹, that reverses the mapping action of f; (formally) given a function f:X→Y, a function g:Y→X such that, ∀x∈X,f(x)=y⟹g(y)=x.

(mathematics) Any function, in the calculus of variations, that satisfies the Euler equations

(astronomy) A relative measure of the relationship between stellar magnitude and the distribution of stars between magnitudes

(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.)