diagraph

A digraph is a pair of letters that together represent a single sound in a language’s writing system. The term comes from the Greek dia- meaning “two” and graphe meaning “writing” or “letter.” Digraphs are a type of grapheme, the smallest unit of writing that maps to a phoneme, and they differ from monographs, which use a single letter for a sound, and from ligatures, which are typographic combinations that may or may not change pronunciation.

Digraphs function as a unit in the orthography of many languages, encoding sounds that cannot be represented by a single letter in a straightforward way. The specific sound a digraph represents varies by language and context. Some digraphs correspond to a common single phoneme, while others have context-dependent pronunciations or may be part of larger letter sequences that produce different sounds in different words.

Common examples in English include ch, which represents /tʃ/ as in chair; sh, representing /ʃ/ as in ship; th, which can stand for /θ/ or /ð/ as in thin or this; ph, for /f/ as in phone; and ng, for /ŋ/ as in ring. The digraph ea can indicate different sounds in different words (as in sea vs. bread). In other languages, digraphs are integral to spelling systems as well; for instance, German uses sch to denote /ʃ/.

In linguistic analysis, digraphs are contrasted with other graphemic units such as trigraphs and multigraphs, and they are central to discussions of phonology, orthography, and literacy.

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