diacritic
US /ˌdaɪ.əˈkrɪt̬.ɪk/
UK /ˌdaɪ.əˈkrɪt̬.ɪk/

1.
signe diacritique, diacritique
a mark, sign, or symbol added to a letter or character to indicate a specific phonetic value, stress, tone, or other linguistic feature
:
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The acute accent is a common diacritic in French.
L'accent aigu est un signe diacritique courant en français.
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Many languages use diacritics to distinguish between words with similar spellings.
De nombreuses langues utilisent des signes diacritiques pour distinguer les mots ayant des orthographes similaires.