Diacritic

A diacritic /daɪ.əˈkrɪtɪk/ – 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.

The main use of diacritical marks in the Latin script is to change the sound-values of the letters to which they are added. Examples from English are the diaereses in naïve and Noël, which show that the vowel with the diaeresis mark is pronounced separately from the preceding vowel; the acute and grave accents, which can indicate that a final vowel is to be pronounced, as in saké and poetic breathèd; and the cedilla under the "c" in the borrowed French word façade, which shows it is pronounced /s/ rather than /k/. In other Latin alphabets, they may distinguish between homonyms, such as the French là ("there") versus la ("the") that are both pronounced /la/. In Gaelic type, a dot over a consonant indicates lenition of the consonant in question.