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).
Sound change is part of the larger process of language change.
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"
- 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 previous sound change causes X,Y > Y (features X and Y merge as Y), a new one 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. The only exeption to this is that a sound change may or may not recognise word boundaries, even when they are not indicated by prosodic clues.
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. This is the traditional view, expressed by the Neogrammarians. In past decades it has been shown that sound change doesn't necessarily affect all the words it in principle could. However, when a sound change is initiated, it usually expands to the whole lexicon given enough time.
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.)
Types of Sound Change
Sound change is informally divided into influenced and spontaneous. Influenced sound changes are sound changes affected by adjacent sounds. Spontaneous sound changes are the opposite. There is some overlap between the two types.
Spontaneous Sound Change
The "Sound Laws" of Grimm and Verner and others are spontaneous sound changes. Another spontaneous sound change transformed Old English [sk] into Middle English [S]. The collapse of many of Middle English's consonant clusters is also a spontaneous sound change. For example, Middle English [kn]>[n] in Modern English.
Influenced Sound Change
There are several types of influenced sound change:
- Assimilation: two adjacent sounds become closer together. Example: the [p] and [b] in "cupboard" became a single [b].
- Dissimilation: the opposite of assimilation, two sounds move farther apart. Example, "February" is now pronounced like "Febyuary".
- Metathesis: two sounds switch places. Example: Old English "thridda" is Modern English "third".
- Tonogenesis: a devoicing of consonants influences the pitch of the vowels, causing tonemes. Example: the rising tone of Mandarin is the reflex of old voiced consonants.
- Liaison: the introduction of a sound between words. Examples: French "il y a" becomes "y a t-il" when inverted. The postvocalic [r] in some English dialects is pronounced only if the following word starts with a vowel.
- Elision, Apocope, and Syncope: these are all loss of sounds. Elision is the loss of unstressed sounds, apocope is the loss of medial sounds, and syncope is final sounds. Elision example: in the southeastern United States, unstressed schwas tend to drop, so "American" is not /@"mEr@k@n/ but /"m@rk@n/. Apocope example: the Old French word for "state" is "estat," but the "s" has dropped since then, yielding, "état." Syncope example: the final "e" in Middle English was pronounced, but was dropped when the next word started with a vowel sound.
- Epenthesis: the introduction of a sound between others. Example: in English, a schwa is sometimes inserted between the diphthongs /OI aI aU/ and following /r l/, so "fire" = /"faI.@r/.
- Prothesis: the addition of a sound to a word. It differs from liaison in that prothesis always affects a word, whereas liaison depends on other words. Example: /s/ + stop clusters in Latin gained a preceding /e/ in Old Spanish and Old French; hence, the Spanish word for "state" is "estado," deriving from Latin "status."
- Haplology: the loss of syllables because nearby syllables sound similar. Example: Old English "Anglaland" became Modern English "England". Haplology would reduce to *haplogy if it was a common word.
- Nasalization: the loss of nasal consonants following vowels in favor of nasalization of the vowel. French "-in" words used to be pronounced [-in], but are now pronounced as [-E~], with the [n] not being pronounced.