That separates or distinguishes; -- applied to points or marks used to distinguish letters of similar form, or different sounds of the same letter, as, ā, ă, ä, ō, &obreve;, etc.
source: Webster 1913
noun
a mark added to a letter to indicate a special pronunciation
source: WordNet 3.0
adjective satellite
capable of distinguishing
Students having superior diacritic powers. The diacritic elements in culture.