"diacritical mark." YourDictionary, n.d. Web. 26 May 2018. <http://www.yourdictionary.com/diacritical-mark>.
diacritical mark. (n.d.). Retrieved May 26th, 2018, from http://www.yourdictionary.com/diacritical-mark
(plural diacritical marks)
(orthography, typography) A symbol in writing used with a letter to indicate a different pronunciation, stress, tone, or meaning, also called "tone marks" when used to indicate tones, e.g. in Vietnamese or pinyin (romanised Mandarin Chinese).