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 Ancient Greek διακριτικός (diakritikós, "distinguishing"), from διακρίνω (diakrī́nō, "to distinguish").

A ring diacritic may appear above or below letters. It may be combined with some letters of the extended Latin alphabets in various contexts.

Els mots composts i derivats d'aquests, com adeu, adeu-siau, marededeu, rodamon, a contrapel, entresol o subsol, no porten l'accent diacrític.. L'accent diacrític en català segons l'AVL