Cheshirization

Cheshirisation, or cheshirization, 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 or  followed in the next syllable. Typically, the or  was then lost, leading to a situation where a trace of the original  or  remains in the fronted quality of the preceding vowel. Alternatively, a distinction formerly expressed through the presence or absence of an or  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 suffix in the (nominative) plural, but had no suffix in the (nominative) singular. A word like "mouse", for example, had a plural  "mice". After umlaut, the plural became pronounced, where the long back vowel was fronted, producing a new subphonemic front-rounded vowel , which serves as a secondary indicator of plurality. Subsequent loss of final, however, made a phoneme and the primary indicator of plurality, leading to a distinction between  "mouse" and  "mice". In this case, the lost sound left a trace in the presence of ; or equivalently, the distinction between singular and plural, formerly expressed through a suffix, has been re-expressed using a different feature, namely the front-back distinction of the main vowel.

Examples
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, from historical.

Other examples:
 * consonant mutation in Celtic languages (a lost vowel triggered initial consonant lenition, and a lost nasal triggered nasalisation);
 * 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 the Estonian language, when case endings are elided, the changed root indicates the presence of the case.

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 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 to, 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.