kernel
ker-nel
noun
The most important, central, or fundamental part of an idea or system.
"That is the kernel of the entire argument."
noun
The softer, edible part found inside a nut, seed, or fruit stone.
"Crack the nut to extract the sweet kernel."
Thesaurus
Synonyms: meat, marrow, heart, center, heart and soul, inwardness, nitty-gritty, essence, nub, substance, pith, centre