Noun
1. the inner and usually edible part of a seed or grain or nut or fruit stone;
"black walnut kernels are difficult to get out of the shell"2. a single whole grain of a cereal;
"a kernel of corn"3. the choicest or most essential or most vital part of some idea or experience;
"the gist of the prosecutor's argument""the heart and soul of the Republican Party""the nub of the story"