A diacritic (; also diacritical mark, diacritical point, diacritical sign from ancient Greek διά (dia, through) and κρίνω (krinein, to separate) is a glyph added to a letter, or basic glyph. The term derives from the Greek διακριτικός (diakritikós, "distinguishing"). Diacritic is both an adjective and a noun, whereas diacritical is only an adjective. Some diacritical marks, such as the acute ( ´ ) and grave ( ` ) are often called accents. Diacritical marks may appear above or below a letter, or in some other position such as within the letter or between two letters.