. "A digraph or digram (from the Greek: \u03B4\u03AF\u03C2 d\u00EDs, \"double\" and \u03B3\u03C1\u03AC\u03C6\u03C9 gr\u00E1ph\u014D, \"to write\") is a pair of characters used to write one phoneme (distinct sound) or a sequence of phonemes that does not correspond to the normal values of the two characters combined. The sound is often, but not necessarily, one which cannot be expressed using a single character in the orthography used by the language."@en . . .