Key

1. When referring to a computer keyboard, a key is a single button on the keyboard. Letters, numbers, functions, and symbols are all represented on keys.
2. A key is also a tool used to lock and unlock a computer, computer drive or other computer related device. If you have lost the key to your computer device, Computer Hope cannot assist you with obtaining a new one. Please contact the manufacturer of the product that is locked. 
3. When referring to the computer Microsoft Windows registry, a registry key, or key for short, is a term used to identify an item in the registry, such as HKEY_LOCAL_MACHINE.
4. The term key or keyed may also be used to describe a cable with physical dimensions that causes a cable such as a ribbon cable to be connected only one direction. In some rare cases this may prevent a cable from being properly connected to a drive. For example, the manufacturer of a floppy disk drive may have keyed their connection differently than the cable manufacturer has. In this situation, the user may either be required to purchase a different brand of cable or floppy drive, or modify the key on the cable.
5. When referring to encryption a key is a set of instructions that is used to encrypt and decrypt data.

Also see: Hard disk drive definitions, Hardware key, Keyboard definitions