CORTEX
1. Anatomy a. The outer layer of an internal organ or body structure, as of the kidney or adrenal gland. b. The outer layer of gray matter that covers the surface of the cerebral hemisphere.

2. Botany The region of tissue in a root or stem lying between the epidermis and the vascular tissue.

3. An external layer, such as bark or rind.

ETYMOLOGY: Latin, bark. See 'sker' in Appendix
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ENTRY: sker

DEFINITION: Also ker-. To cut.

EXTENDED ROOTS: *skert-, *kert-.
Zero-grade form *kt- or o-grade form *kort-. cortex; decorticate, from Latin cortex, bark (“that which can be cut off”).

Source:
The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.