Longman Dictionary of Contemporary English
Wiktionary
n. (context computing English) Any of a set of keys on a personal computer or terminal keyboard used to activate a predefined or programmable function.
Wikipedia
A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions, a form of soft key. On some keyboards/computers, function keys may have default actions, accessible on power-on.
Function keys on a terminal may either generate short fixed sequences of characters, often beginning with the escape character ( ASCII 27), or the characters they generate may be configured by sending special character sequences to the terminal. On a standard computer keyboard, the function keys may generate a fixed, single byte code, outside the normal ASCII range, which is translated into some other configurable sequence by the keyboard device driver or interpreted directly by the application program. Function keys may have (abbreviations of) default actions printed on/besides them, or they may have the more common "F-number" designations.
Usage examples of "function key".
Honor reached out to the arm of his command chair and tapped a function key, throwing one of the evasion patterns she'd entered at DuChene's station onto McKeon's repeater plot.
On what had to be the command level was a continuous circumferential bench four feet from the floor without so much as a screen or a function key to mar its smooth surface.
And if this expert was so good, maybe he could figure out which function key controlled the security satellite bypass and how Klonski-Boronov had managed to scramble supposedly tamperproof chips.
He told the computer he wanted to change the program: he pressed the VERB function key, and then 3, 7, ENTER.
She tapped a function key, and Prescott smiled a shark's smile as he watched her display.
She touched another function key, and three more light codes suddenly grew white rims.
Johnnie snapped open the cover of his own controls, slid the magenta cursor along the docks with his joystick, and began tapping a function key.
He brushed the bag aside on his way to the console, punched a function key.