A diacritic – also diacritical mark, diacritical point, or diacritical sign – is a glyph added to a letter, or basic glyph. The term derives from the Greek διακριτικός (diakritikós, "distinguishing"), which is composed of the ancient Greek διά (diá, through) and κρίνω (krínein or kríno, to separate). Diacritic is primarily an adjective, though sometimes used as a noun, whereas diacritical is only ever 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.