The core, center, or essence of an object or system. • The central (usually edible) part of a nut, especially once the hard shell has been removed. • A single seed of grain, especially of corn or wheat. • The stone of certain fruits, such as peaches or plums. • A small mass around which other matter is concreted; a nucleus; a concretion or hard lump in the flesh. • The central part of many computer operating systems which manages the system's resources and the communication between hardware and software components. • The core engine of any complex software system. • The simplified input to an algorithm that has undergone kernelization. • A function used to define an integral transform. • The set of pairs of elements in the domain of f which are mapped to the same value; the equivalence relation x≡y⟺f(x)=f(y). • The set of elements of the domain of f which are mapped to an identity element. • The set of elements of G which are mapped to the identity of H (usually written as 0 in an additive group and as 1 in a multiplicative group). • The set of elements of R which are mapped to the additive identity 0 of S. • The set of elements of M which are mapped to the additive identity 0 of N. • The equalizer of f and the zero morphism from X to Y, denoted operatorname kerf. • The source of operatorname kerf, denoted operatorname Kerf. • The set of members of a fuzzy set that are fully included (i.e., whose grade of membership is 1). • The human clitoris. • The nucleus and electrons of an atom excluding its valence electrons.