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.
1690s, of sounds, from Greek diakritikos "that separates or distinguishes," from diakrinein "to separate one from another," from dia- (see dia-) + krinein "to separate, decide, judge" (see crisis). As a noun, from 1866. Related: Diacritical.