(astronomy, mathematics) A relationship that describes the mass distribution.

(systems theory) A function that controls the recording, processing, transmission, or interpretation of data.

(mathematics) a completely multiplicative function on the positive integers that is defined as equal to one for a special value and zero otherwise:

(mathematics) A formal power series with one indeterminate, whose coefficients encode a sequence that can be studied by algebraic manipulation of the series; any one of several generalizations, such as to encode more than one sequence or use more than one indeterminate.

(mathematics) Either of two functions that are solutions to Bessel's equation.

(mathematics) a function used to calculate the distance between two points. / (topology) a metric.

(mathematics) A function used to predict a categorical dependent variable by one or more continuous or binary independent variables.

(number theory) A function, denoted by ρ, used to estimate the proportion of smooth numbers up to a given bound.

(programming) An anonymous function; a function that is defined in an inline, ad-hoc manner, and often doesn't have a name (not bound to an identifier).

(mathematics) A Schur polynomial. / (mathematics) A holomorphic function in the Schur class.