a mark such as an accent, placed over, under, or through a letter in some languages, to show that the letter should be pronounced in a different way from the same letter without a mark
NAmE//ˌdaɪəˈkrɪt̮ɪkl//
adjective diacritical marksSee diacritic in the Oxford Advanced Learner's DictionaryCheck pronunciation: diacritic