In historical linguistics, it is concerned with the reflexes of an ancestral phoneme as a language splits into dialects, such as the modern realizations of Old English /oː/.
[18] The linguistic variable, a similar[19] concept presented by William Labov, refers to features with variations that are referentially identical but carry social and stylistic meaning.
[22] The latter concept met resistance from scholars for a number of reasons[23] including the argument from critics that knowledge of rule probabilities was too far from speakers' competence.
[27] Inspired by Trubetzkoy (1931), Uriel Weinreich first advocated the use of diasystems in structural dialectology, and suggested that such a system would represent a higher level of abstraction that can unite related dialects into a single description and transcription.
Saporta (1965:220) suggests that the rules needed to account for dialectal differences, even if not psychologically real, may be historically accurate.
[37] Weinreich (1954) argued that Trager & Smith (1951) fell short in accurately representing dialects because their methodology involved attempting to create a diasystem before establishing the relevant component phonemic systems.
In addition, both Wells and Weinreich mention realizational overlap, wherein the same phone (or a nearly identical one) corresponds to different phonemes, depending on accent.
In order to accommodate both pronunciations, the basic letter of Meccan Arabic was used, but the diacritic was dropped: ى.
For example, the Spanish of Los Ojos (a small village in Rio Arriba County, New Mexico) and the local variety of Southwestern English are fairly isomorphic with each other[51] so a diaphonic approach for such a language contact situation would be relatively straightforward.
[53] Similarly, Shen (1952), argues that phonemic representations may lead to confusion when dealing with phonological interference and Nagara (1972:56) remarks that narrow phonetic transcription can be cumbersome, especially when discussing other grammatical features like syntax and morphology.
[54] Similarly, the term diaphone can be used in discussions of cognates that occur in different languages due to borrowing.
Specifically, Haugen (1956:46, 67) used the term to refer to phonemes that are equated by speakers cross-linguistically because of similarities in shape and/or distribution.
[57] In these interlanguage transfers, when phonemes or phonotactic constraints are too different, more extreme compromises may occur; for example, the English phrase Merry Christmas, when borrowed into Hawaiian, becomes mele kalikimaka.
[58] The process of diaphonic identification occurs when pidgins are fashioned; although lexical and morphosyntactic patterns are shared, speakers often use the phonological systems of their native language, meaning they must learn to recognize such diaphonic correspondences in the speech of others to facilitate the mutual intelligibility of a working pidgin.
[59] Bailey (1971) proposes that rule differences can be used to determine the distance a particular utterance has between a post-creole continuum's acrolectal and basolectal forms.
The status of panlectal and polylectal grammars[c] has been subject to debate amongst generative phonologists since the 1970s;[60][61] one of the foremost areas of contention in regards to diaphonemes and diasystems is whether they reflect the actual linguistic competence of speakers.
[62] Peter Trudgill argues against the formation of diasystems that are not cognitively real[63] and implies[64] that polylectal grammars that are not part of native speakers' competence are illegitimate.
[75] John Wells argues that going past the common core creates difficulties that add greater complexity and falsely assume a shared underlying form in all accents:[76] Only by making the diaphonemic representation a rather remote, underlying form, linked to actual surface representations in given accents by a long chain of rules–only in this way could we resolve the obvious difficulties of the taxonomic diaphoneme.Wells gives the example of straight, late and wait, which rhyme in most English varieties but, because some dialects make phonemic contrasts with the vowels of these words (specifically, in parts of the north of England[d]), a panlectal transcription would have to encode this contrast despite it being absent for most speakers, making such a system "a linguist's construct"[77] and not part of the grammar present in any native speaker's mind (which is what adherents of such a system attempt to achieve).
[86][87] Berdan (1977) argues that comprehension across varieties, when it is found, is insufficient evidence for the claim that polylectal grammars are part of speakers' linguistic competence.
[90] Similarly, the diaphonemic system in Geraghty (1983) goes beyond the common core, marking contrasts that only appear in some varieties;[91] Geraghty argues that, because of Fijian marriage customs that prompt exposure to other dialects, speakers may possess a diasystem that represents multiple dialects as part of their communicative competence.
One way is through the IPA, this can be done with slashes, as if they are phonemes, or with other types of brackets: The concept does not necessitate the formation of a transcription system.
[100] Even in dialectology, diaphonemic transcriptions may instead be based on the language's orthography, as is the case with Lee Pederson's Automated Book Code designed for information from the Linguistic Atlas of the Gulf States[101][102] and the diaphonemic transcription system used by Paul Geraghty for related Fijian languages uses a modified Roman script.