A digraph or digram (from the Greek: δίς dís, "double" and γράφω gráphō, "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.
Digraphs are often used for phonemes that cannot be represented using a single character, like the English sh in ship and fish. In other cases they may be relics from an earlier period of the language when they had a different pronunciation, or represent a distinction which is made only in certain dialects, like English wh. They may also be used for purely etymological reasons, like rh in English. Digraphs are used in some Romanization schemes, like the zh often used to represent the Russian letter ж. As an alternative to digraphs, orthographies and Romanization schemes sometimes use letters with diacritics, like the Czech š, which has the same function as the English digraph sh.
In some languages' orthographies, digraphs (and occasionally trigraphs) are considered individual letters, meaning that they have their own place in the alphabet, and cannot be separated into their constituent graphemes, e.g. when sorting, abbreviating or hyphenating. Examples are found in Hungarian (cs, dz, dzs, gy, ly, ny, sz, ty, zs), Czech (ch), Slovak (ch, dz, dž), Albanian (dh, gj, ll, nj, rr, sh, th, xh, zh) and Gaj's Latin Alphabet (lj, nj, dž). In Dutch, when the digraph ij is capitalized, both letters are capitalized (IJ).
Digraphs may develop into ligatures, but these are distinct concepts – a ligature involves a graphical combination of two characters, as when a and e are fused into æ.
