definition digraph
A digraph or digram (from the Greek: Î´Î¯Ï dÃ­s, double and Î³ÏÎ¬ÏÏ grÃ¡phÅ, to write) is a pair of characters used in the orthography of a language to write either a single phoneme (distinct sound), or a sequence of phonemes that does not correspond to the normal values of the two characters combined.