outer layer
外层
例句与用法：
Having a cortex or a similar specialized outer layer.
有皮的有皮的或具有相似的专门发育的外部覆盖的
An outer layer or coating applied to a surface for protection or decoration.
饰面，保护面装在外面的外层或薄层，为了保护或装饰
The outer layer of an internal organ or body structure, as of the kidney or adrenal gland.
皮层内部器官或身体结构的外层，如肾或肾上腺皮层