Sound change

Sound change or phonetic change is a historical process of language change consisting in the replacement of one speech sound or, more generally, one phonetic feature by another in a given phonological environment. Sound change is supposed to be regular, which means that it should be expected to apply mechanically whenever its structural condition is met, irrespective of any non-phonological factors (such as the meaning of the words affected). Hence the somewhat hyperbolic term sound law, introduced in the 19th c. and still applied traditionally to some of the historically important sound changes, e.g. Grimm's law. While real-world sound changes often admit of exceptions (for a variety of known reasons, and sometimes without a known reason), the expectation of their regularity or "exceptionlessness" is of great heuristic value, since it allows historical linguists to define the notion of regular correspondence (see: comparative method).

The formal notation of sound change:

A > B

is to be read, "A changes into (or is replaced by, is reflected as, etc.) B". It goes without saying that A belongs to an older stage of the language in question, whereas B belongs to a more recent stage. The symbol ">" can be reversed:

B < A

"(more recent) B derives from (older) A"

For example,

POc. *t > Rot. f

= "Proto-Oceanic *t is reflected as [f] in the Rotuman language." This is actually a compressed account of a sequence of changes (*t changed first into a dental fricative [T] like the initial consonant of English thin, which has yielded present-day [f]).

Unless a change operates unconditionally (in all positions), we have to specify the context in which it applies:

A > B /X__Y

= "A changes into B when preceded by X and followed by Y." For example:

It. b > v /[vowel]__[vowel]

= "Intervocalic /-b-/ (inherited from Latin) became /-v-/ in Italian" (e.g. in caballum, de:bet > cavallo 'horse', deve 'owe (3sg.)'

PIr. [-cont] > [+cont]/[__,-voice]C

= "Preconsonantal voiceless non-continuants (i.e. voiceless stops) changed into corresponding voiceless continuants (fricatives) in Proto-Iranian", so that e.g. Proto-Indo-European *pr, *pt > Proto-Iranian *fr, *ft (features not mentioned explicitly in the formulation of the change, such as the place of articulation, are assumed not to change).

If the symbol "#" stands for a word boundary (initial or final), the notation "/__#" = "word-finally", and "/#__" = "word-initially". For example:

Gk. [stop] > zero /__#

= "Word-final stops were deleted (replaced by zero) in Greek."

Rules of Sound Change

Sound change has no memory Sound change does not discriminate between the sources of a sound. If a sound change causes X>Y, it cannot affect only original X's. If it helps, think of a stampede of animals, each erasing its predecessor's footprints.

Sound change ignores grammar A sound change can only have phonological restraints, like X>Z in unstressed syllables. It cannot drop final W, except on adjectives, or the like.

Sound change is exceptionless If a sound can happen at a place, it will. It affects all sounds that meet the criteria for change. Exceptions are possible, due to either analogy and other regularization processes, or another sound change.

Sound change is unstoppable Nobody knows why, but all languages invariably vary from place to place and time to time. Writing does not keep languages from changing. This would be true if we learnt languages from reading books. We don't. We learn our native tongue by imitating the speakers in our environment. Only dead languages, artificially resurrected and kept alive languages like Latin, and international languages like Esperanto are immune to sound change. (The only thing that has stopped Esperanto from having dialects is the fact that it is almost entirely second-language speakers. If they speak it to their children, and they do the same and so on, sound change WILL happen.)