skin

皮(かわ)	Skin, (human or animal, but not to be confused with fur, which is 毛皮!). Also the skin of an apple, or even the crust of bread! $$$

肌(はだ)	Refers to the skin of a person – not to leather or animal skin.

皮膚(ひふ)	Skin (doctor word – like the English ‘epidermis’).

革(かわ)	Leather.