(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.

(mathematical analysis) A function which is Borel measurable.

(mathematics) A linear mapping from a vector space to its field of scalars.

(physiology) A normal physical process that occurs in the body. / (euphemistic) An excretory function of an organism, usually the discharging of feces and urine.

A real-valued function on a differentiable manifold such that, at each point in its domain where the function's differential is zero, the function's Hessian is nonsingular.

(medicine) The remaining capacity of an organ or body part to fulfil its physiological activity; (especially) in the context of disease, ageing, or impairment.

(biology) Any function of the body that is essential for maintaining life, especially breathing and circulation.

(computing, database normalization) A constraint between two sets of attributes in a relation.

plural of functional requirement

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