grapheme

A grapheme (from the Greek: γράφω, gráphō, "write") is a fundamental unit in a written language. Examples of graphemes include alphabetic letters, Chinese characters, numerical digits, punctuation marks, and the individual symbols of any of the world's writing systems, although arguably^{[citation needed]} a diacritical mark or ancillary glyph does not constitute a grapheme.

In a fully phonemic orthography, a grapheme corresponds to one phoneme. However this is very much the exception. In spelling systems that are to some extent non-phonemic, such as in English, multiple graphemes may represent a single phoneme. These are called digraphs (two graphemes for a single phoneme) and trigraphs (three graphemes). For example, the word ship contains four graphemes (s, h, i, and p) but only three phonemes, because sh is a digraph. Conversely, a single grapheme can represent multiple phonemes, or no phonemes at all in the case of 'silent' letters: the English word "box" has three graphemes, but four phonemes: /bɒks/.