dongle

A dongle is a small piece of computer hardware that connects to a port on another device to provide it with additional functionality, or enable a pass-through to such a device that adds functionality.In computing, the term was initially synonymous with software protection dongles—a form of hardware digital rights management where a piece of software will only operate if a specified dongle—which typically contains a license key or some other cryptographic protection mechanism—is plugged into the computer while it is running.
The term has since been applied to other forms of devices with a similar form factor, such as:

adapters that convert ports to handle different types of connectors (such as DVI to VGA for displays, USB-to-serial data communication, and in modern computing, USB-C to other types of ports, and Mobile High-Definition Link),
USB wireless adapters for standards such as Bluetooth and Wi-Fi
USB flash drives (more commonly described as "USB stick" or "USB key")
small form-factor digital media players that plug into HDMI ports (most commonly described as a "media player dongle" or "media player stick")

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