|Sound change and alternation|
Cheshirization, or cheshirisation, is a term coined by James Matisoff to refer to a type of sound change where a trace remains of a sound that has otherwise disappeared from a word. The term is a neologism, i.e. it is not an established scientific term. It is used here to describe a process that is real but so far has no generally accepted name. The term rephonologization has sometimes been used to describe this process; see below.
Essentially, a distinction between two sets of words that was formerly expressed through one phonological feature (e.g. a particular sound) is preserved (or partly preserved) through being re-expressed using a different phonological feature. This typically occurs through two sound changes: One that introduces a modification of some sort, conditioned on the presence or absence of a particular feature, followed by another change that deletes or changes the conditioning feature.
A common example is Germanic umlaut. In many Germanic languages around 500–700 AD, a sound change fronted a back vowel when an /i/ or /j/ followed in the next syllable. Typically, the /i/ or /j/ was then lost, leading to a situation where a trace of the original /i/ or /j/ remains in the fronted quality of the preceding vowel. Alternatively, a distinction formerly expressed through the presence or absence of an /i/ or /j/ suffix was then re-expressed as a distinction between a front or back vowel.
As a specific instance of this, in prehistoric Old English, a certain class of nouns was marked by an /i/ suffix in the (nominative) plural, but had no suffix in the (nominative) singular. A word like /muːs/ "mouse", for example, had a plural /muːsi/ "mice". After umlaut, the plural became pronounced [myːsi], where the long back vowel /uː/ was fronted, producing a new subphonemic front-rounded vowel [yː], which serves as a secondary indicator of plurality. Subsequent loss of final /i/, however, made /yː/ a phoneme and the primary indicator of plurality, leading to a distinction between /muːs/ "mouse" and /myːs/ "mice". In this case, the lost sound /i/ left a trace in the presence of /yː/; or equivalently, the distinction between singular and plural, formerly expressed through a suffix /i/, has been re-expressed using a different feature, namely the front-back distinction of the main vowel. This distinction survives in the modern forms "mouse" /maʊs/ and "mice" /maɪs/, although the specifics have been modified by the Great Vowel Shift.
Before disappearing, a sound may trigger or prevent some phonetic change in its vicinity that would not otherwise have occurred, and which may remain long afterward. For example :
- In the English word night, the gh sound disappeared, but before or perhaps as it did so it lengthened the vowel i, so that the word is pronounced // "nite" rather than the // "nit" that would otherwise be expected for a closed syllable.
- In French, a final n sound disappeared, but left its trace in the nasalization of the preceding vowel, as in vin blanc [vɛ̃ blɑ̃], from historical [vin blaŋk].
- consonant mutation in Celtic languages (a lost vowel triggered initial consonant lenition, and a lost nasal triggered nasalization);
- the prevention of sound change by a lost consonant in Lahu;
- floating tones, which are the remains of entire disappeared syllables;
- and the tone split of Chinese languages, where voiced consonants lowered the tone of a syllable and subsequently lost their voicing.
- In Estonian and some other Uralic languages, when case endings are elided, the changed root indicates the presence of the case, see consonant gradation.
The term cheshirization refers to the Cheshire Cat, a character in the book Alice in Wonderland, who "vanished quite slowly, beginning with the end of the tail, and ending with the grin, which remained some time after the rest of it had gone."
Other names 
In a 1994 paper, Norman used the term rephonologization to refer to the same type of process, in the context of a proposed Old Chinese sound change that transferred a distinction formerly expressed through putative pharyngealization of the initial consonant of a syllable to one expressed through presence or absence of a palatal glide /j/ before the main vowel of the syllable. Note that rephonologization is occasionally used with another meaning, referring to changes such as the Germanic sound shift or the Slavic change from /ɡ/ to /ɦ/, where the phonological relationships among sounds change but the number of phonemes stays the same. This can be viewed as a special case of the broader process being described here.
See also 
- Norman, Jerry (July–September 1994). "Pharyngealization in Early Chinese". Journal of the American Oriental Society 114: 397–408. Specifically, the glide /j/ occurred whenever the initial consonant was not pharyngealized.
- Trask, R.L. (1995). A Dictionary of Phonetics and Phonology. Routledge. ISBN 978-0-415-11261-1.
- James Matisoff, 1991, "Areal and universal dimensions of grammatization in Lahu." In Approaches to grammaticalization, Traugott & Heine, eds. John Benjamins, pp 383–453.
- Östen Dahl, 2004, The Growth and Maintenance of Linguistic Complexity. John Benjamins, p. 170.
- Hilary Chapell, 2006, "Language contact and areal diffusion in Sinitic languages." In Areal diffusion and genetic inheritance: problems in comparative linguistics., Aleksandra Aikhenvald & Robert M. W. Dixon, eds. Oxford University Press, p. 344.
- John H. McWhorter, Defining Creole, Oxford University Press, p. 12-13.