Kernel

amande

(central part of a nut)

cerneau

(central part of a nut)

cœur

(core or essence of an object or system)

fond

(core or essence of an object or system)

grain

(single seed of corn or wheat)

noyau

((US) stone of certain fruits, such as peaches or plums)

noyau

((computing) central part of many computer operating systems)

noyau

((mathematics, algebra) set of elements mapped to zero)