a.

1. 圆周的
2. 周围的；外面的
3. 【解】体表的；（神经）末梢的
4. 次要的

n.

1. 【电脑】外部设备

adj.

1. relating to or situated on the periphery.
2. marginal.
3. (of a device) able to be attached to and used with a computer, though not an integral part of it.
4. Anatomy  near the surface of the body.

n.