A digraph (en français, digramme ; em português, dígrafo) is two characters written to make one sound (phoneme). The Latin-based orthographies for many languages include digraphs. In some orthographies, the digraphs are treated as single characters in collation.
Wikipedia, "Dígrafo," http://pt.wikipedia.org/wiki/Dígrafo
______, "Digramme," http://fr.wikipedia.org/wiki/Digramme
______, "Digraph (orthography)," http://en.wikipedia.org/wiki/Digraph_%28orthography%29
