Definition: Any auxiliary device such as a mouse, keyboard, hard drive, etc. that connects to and works with the computer in some way. Usually, a peripheral refers to a device external to the computer, like a scanner, even though peripherals may be located inside the computer case.
Also Known As: external peripheral, auxiliary component
Examples:
"Many of the external peripherals I own, such as my scanner and printer, connect to the peripheral ports on the back of my computer."

