scriptphoneme

Scriptphoneme is a theoretical unit used in linguistics to describe the smallest orthographic realization of a phoneme within a particular writing system. A scriptphoneme may be realized by a single letter, such as 'f' for the phoneme /f/ in many English words, or by a sequence of letters, such as 'ph' in 'phone' or 'ch' in some languages. Because orthographies differ across languages, the same phoneme may have multiple scriptphonemes in different scripts.

Unlike a grapheme, which is a general unit of written language, a scriptphoneme emphasizes a one-to-one mapping to a phoneme within a given script and thus can be multi-letter. A phoneme, by contrast, is an abstract sound; a scriptphoneme is a written instantiation of that sound. Because of allophony and context, a single phoneme may be realized by different scriptphonemes in different positions or words, and a scriptphoneme may correspond to more than one phoneme in other scripts.

In computational linguistics, scriptphoneme can be useful as an intermediate representation in grapheme-to-phoneme conversion, corpus annotation, and orthography design. It helps formalize how a language's phoneme inventory maps onto its writing system, particularly for digraphs, diacritics, and language-specific spelling rules. The concept is most helpful when comparing orthographies or when building pronunciation models across languages.

Limitations include ambiguity in boundaries between scriptphonemes, especially in languages with rich allomorphy or variable spelling. The inventory of scriptphonemes is not universal and can change with orthographic reforms. Because scriptphoneme is not a universally standardized term, its precise definition can vary among researchers and languages.