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.
Surge definition, a strong, wavelike, forward movement, rush, or sweep: the onward surge of an angry mob. See more.
The LH surge is a signal from the brain to the ovary that an egg is mature. The brain senses the elevated estrogen levels produced by the maturing egg and releases a burst of luteinizing hormone (LH).