Diacritic

In several writing systems, a diacritic—also called diacritic(al) mark or diacritic(al) sign— is a little sign added on a character, modifying slightly this character, in order to give any information about the pronunciation or, sometimes, in order to distinguish a word from another word. For instance: the letter e becomes é, c becomes č, o becomes ø, s becomes ș, ω becomes ώ, и becomes й.