n.

1. （果核或果壳内的）仁[C]
2. （麦、玉米等的）粒，子[C]
3. 【喻】核心，要点[the S][（+of）]
   the true kernel of the matter

   这件事的真正核心

vt.

1. 把……包在核（或壳）内；把……作核心

n.

1. a softer part of a nut, seed, or fruit stone contained within its hard shell.
   ▸the seed and hard husk of a cereal, especially wheat.
2. the central or most important part of something.
   ▸Computing  the most basic level or core of an operating system.