1. (in botany) The tissue between the epidermis and the vascular system in plant stems and roots. It is composed of parenchyma cells and shows little or no structural differentiation. Cortex is produced by activity of the apical meristem. See also endodermis.

2. (in zoology) The outermost layer of tissue of various organs, including the adrenal glands (adrenal cortex), kidneys (renal cortex), and cerebral hemispheres (cerebral cortex).