A Bark

1. (ountable, uncountable) The exterior covering of the trunk and branches of a tree.
2. (medicine) Peruvian bark or Jesuit's bark, the bark of the cinchona from which quinine is produced.
3. Hard candy made in flat sheets, for instance out of chocolate, peanut butter, toffee or peppermint.
4. The envelopment or outer covering of anything.

Usually uncountable; bark may be countable when referring to the barks of different types of tree.

(exterior covering of a tree): rind