kernel

noun

1. The core, center, or essence of an object or system.

   “the kernel of an argument”

2. The central (usually edible) part of a nut, especially once the hard shell has been removed.
3. A single seed of grain, especially of corn or wheat.
4. (US)The stone of certain fruits, such as peaches or plums.
5. A small mass around which other matter is concreted; a nucleus; a concretion or hard lump in the flesh.
6. The central part of many computer operating systems which manages the system's resources and the communication between hardware and software components.

   “The Linux kernel is open-source.”

7. The core engine of any complex software system.
8. The simplified input to an algorithm that has undergone kernelization.
9. A function used to define an integral transform.

   “The Dirichlet kernel convolved with a function yields its Fourier series approximation.”

10. 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).

    “If a function is continuous then its kernel is a closed set.”

11. (broadly)The set of elements of the domain of f which are mapped to an identity element.
12. (broadly)The set of elements of the domain of f which are mapped to an identity element.
13. (broadly)The set of elements of the domain of f which are mapped to an identity element.
14. The equalizer of f and the zero morphism from X to Y, denoted operatorname kerf.
15. The equalizer of f and the zero morphism from X to Y, denoted operatorname kerf.
16. The set of members of a fuzzy set that are fully included (i.e., whose grade of membership is 1).
17. (slang)The human clitoris.

    “Using the blunt end of one of the vibraphone mallets, he pried open her folds. With the balled end of the other, he rhythmically rolled over her kernel.”

18. The nucleus and electrons of an atom excluding its valence electrons.

    “1. In every atom is an essential kernel which remains unaltered in all ordinary chemical changes and which possesses an excess of positive charges corresponding in number to the ordinal number of the group in the periodic table to which the element belongs.”

verb

1. To enclose within a kernel
2. To crenellate