kernel

plural kernels

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

   the kernel of an argument

   Synonyms: crux, gist, bowels, sum, brass tacks, core, crux, essence

2. biologyThe central (usually edible) part of a nut, especially once the hard shell has been removed.
3. biologyA single seed of grain, especially of corn or wheat.
4. USbiologyThe 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. computingThe 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.

   Antonyms: userland

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

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

10. mathematicsThe 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. The set of elements of the domain of f which are mapped to an identity element.
    1. broadlyalgebraThe 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).

       Antonyms: support

    2. broadlyring theoryalgebraThe set of elements of R which are mapped to the additive identity 0 of S.

       Antonyms: support

    3. broadlyalgebraThe set of elements of M which are mapped to the additive identity 0 of N.

       Antonyms: support

12. category theoryThe equalizer of f and the zero morphism from X to Y, denoted operatorname kerf.
    1. category theoryThe source of operatorname kerf, denoted operatorname Kerf.
13. fuzzy set theorymathematicsThe set of members of a fuzzy set that are fully included (i.e., whose grade of membership is 1).
14. slangThe 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.

    2014, Karyn Gerrard, Irene Preston, Lotchie Burton, et al: Summer Heat: 10 Spicy Romances That Sizzle

15. chemistryThe 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.

    1916, Gilbert N. Lewis, “The Atom and The Molecule”, in Journal of the American Chemical Society, 38(4) p 768

16. figurativelyA seed, metaphorically: a concept or principle with a distinct essence that exists within a larger context and has potential for growth, development, and propagation, by the same mental model as a seed of doubt or a kernel of truth (grain of truth), and comparable to a nugget (of wisdom, advice, etc) or a pearl (such as a pearl of wisdom).

    The drumbeat of warning that advanced AI could kill us all has mostly quieted; the “doomers” have been marginalized, now used by AI’s ruling class as a punch line. Yet even the most upbeat AI leaders are quick to offer kernels of warning.

    2025 December 11, Charlie Campbell, Andrew R. Chow and Billy Perrigo, “The Architects of AI Are TIME’s 2025 Person of the Year”, in Time

17. fossil onlyagricultureSynonym of seedling (“plant variety from seedling origin”).

    Ashmead's Kernel

    Synonyms: seedling

present singular third person kernels · US participle present kerneling · UK participle present kernelling · US participle past kerneled · US past kerneled · UK participle past kernelled · UK past kernelled

1. To enclose within a kernel
2. To crenellate