Dead key
A dead key is a special kind of a modifier key on a mechanical typewriter, or computer keyboard, that is typically used to attach a specific diacritic to a base letter. The dead key does not generate a (complete) character by itself, but modifies the character generated by the key struck immediately after. Thus, a dedicated key is not needed for each possible combination of a diacritic and a letter, but rather only one dead key for each diacritic is needed, in addition to the normal base letter keys.
For example, if a keyboard has a dead key for the grave accent (), the French character à can be generated by first pressing and then A, whereas è can be generated by first pressing and then E.Usually, the diacritic itself can be generated as an isolated character by pressing the dead key followed by space; so a plain grave accent can be typed by pressing and then Space.