Nub
Part of speech: noun
Definition: The essence or core of something. A small lump or knob. The clitoris. A noob; a newcomer or incompetent.
Essence
Part of speech: noun
Definition: The inherent nature of a thing or idea.A significant feature of something.The concentrated form of a plant or drug obtained through a distillation process.Fragrance, a perfume.The true nature of anything, not accidental or illusory.
Example sentence: Battle is the most magnificent competition in which a human being can indulge. It brings out all that is best; it removes all that is base. All men are afraid in battle. The coward is the one who lets his fear overcome his sense of duty. Duty is the essence of manhood.