Also called diacritical mark.a mark, point, or sign added or attached to a letter or character to distinguish it from another of similar form, to give it a particular phonetic value, to indicate stress, etc., as a cedilla, tilde, circumflex, or macron.
n. A mark, such as the cedilla of façade or the acute accent of resumé, added to a letter to indicate a special phonetic value or distinguish words that are otherwise graphically identical.
[Greek diakritikos, distinguishing, from diakritos, distinguished, from diakrīnein, to distinguish : dia-, apart; see dia- + krīnein, to separate; see krei- in Indo-European roots.]