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 International Phonetic Alphabet (IPA) is a system of phonetic notation devised by linguists to accurately and uniquely represent each of the wide variety of sounds (phones or phonemes) used in spoken human language. ... Phonetic (pho-NET-ic) is a nationwide voicemail-to-text messaging service available for most digital mobile phones in which a subscriber is provided a custom voice mailbox for the purpose of receiving all incoming voice messages as actual transcribed text for reading via short messaging (also known as SMS... Due to technical limitations, some web browsers may not display some special characters in this article. ... This is a concise version of the International Phonetic Alphabet for English sounds. ... Grimms law (also known as the [First] Germanic Sound Shift) was the first non-trivial systematic sound change ever to be discovered; its formulation was a turning-point in the development of linguistics, enabling the introduction of rigorous methodology in historical linguistic research. ... The comparative method (in linguistics) is a method used to detect genetic relationships between languages and to establish a consistent relationship hypothesis by reconstructing: the common ancestor of the languages in question, a plausible sequence of regular changes by which the historically known languages can be derived from that common...

Each sound change is limited in space and time. It means it functions within a specified area (only in some dialects / ethnolects) and within a specified period of time. These limitations are one of the reasons for which some scholars refuse using the term "sound law" (asserting that laws should not have such spatial and temporal limitations) and replace it with phonetic rule. A dialect (from the Greek word διάλεκτος, dialektos) is a variety of a language used by people from a particular geographic area. ... Ethnolect is a variant of a language spoken by a certain ethnic/cultural subgroup and distinguishing them as a mark of social identity. ...

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"

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 [θ] 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: The Oceanic languages are a subgroup of the Austronesian languages, containing approximately 450 languages. ...

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, dēbet > 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: Fricatives (or spirants) are consonants produced by forcing air through a narrow channel made by placing two articulators close together. ...

Gk. [stop] > ∅ /__#

= "Word-final stops were deleted in Greek."

Rules of sound change

The following statements are used as heuristics in formulating sound changes as understood within the Neogrammarian model. However, for modern linguistics, they are not taken as inviolable rules; rather, they are seen as guidelines. The Neogrammarians (also Young Grammarians, German Junggrammatiker) were a German school of linguists, originally at the University of Leipzig, in the late 19th century who proposed the Neogrammarian hypothesis of the regularity 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 constraints, like X > Z in unstressed syllables. It cannot drop final W, except on adjectives, or the like. The only exception to this is that a sound change may or may not recognise word boundaries, even when they are not indicated by prosodic clues. Also, sound changes may be regularized in inflectional paradigms (such as verbal inflection), in which case the change is no longer phonological but morphological in nature. Prosody may mean several things: Prosody consists of distinctive variations of stress, tone, and timing in spoken language. ... The vowels of modern (Standard) Arabic and (Israeli) Hebrew from the phonological point of view. ... Morphology is the following: In linguistics, morphology is the study of the structure of word forms. ...

Sound change is exceptionless: If a sound can happen at a place, it will. It affects all sounds that meet the criteria for change. Apparent exceptions are possible, due to analogy and other regularization processes, or another sound change, or an unrecognized conditioning factor. 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. Analogy is either the cognitive process of transferring information from a particular subject (the analogue or source) to another particular subject (the target), or a linguistic expression corresponding to such a process. ... A lexicon is usually a list of words together with additional word-specific information, i. ...

Sound change is unstoppable: Nobody knows why, but all languages 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 do not. We learn our native tongue by imitating the speakers in our environment. Only dead languages are immune to sound change. Perhaps the best explanation is to note that everything changes, and language is one part of everything. An extinct language is a language which is no longer natively spoken: it is estimated that one natural human language dies every two weeks. ...

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 [ʃ]. 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. Grimms law (also known as the [First] Germanic Sound Shift) was the first non-trivial systematic sound change ever to be discovered; its formulation was a turning-point in the development of linguistics, enabling the introduction of rigorous methodology in historical linguistic research. ... It has been suggested that Grammatischer Wechsel be merged into this article or section. ...

Conditioned sound change

There are several types of conditioned sound change, that is, sound changes that occur due to specific conditioning factors.

• Assimilation: One sound becomes more like another, or two sounds become more like each other. Example: the [p] and [b] in "cupboard" became a single [b].

• Dissimilation: The opposite of assimilation. One sound becomes less like another, or two sounds become less like each other. Example: The first half of the first vowel in Middle English bite [biitə] has gradually grown less and less like the second half: [ii] > [əi] > [ai] > [ɑi] in modern English bite.

• Metathesis: Two sounds switch places. Example: Old English thridda has become Modern English third.

• Tonogenesis: Syllables come to have distinctive pitch countours. Final consonants lenite, with stops becoming [ʔ] and fricatives becoming [h]. These sounds affect the pitch contour of the previous syllable, and at some point, speakers take the countours (i.e., tones) as primary, rather than the consonants, which are subsequently lost.

• Liaison: The introduction of a sound between words. Examples: French "il y a" becomes "y a t-il" when inverted. The postvocalic [ɹ] in some English dialects is pronounced only if the following word starts with a vowel.

• Elision, Apocope, and Syncope: All losses of sounds. Elision is the loss of unstressed sounds, apocope is the loss of final sounds, and syncope is the loss of medial sounds. Elision example: in the southeastern United States, unstressed schwas tend to drop, so "American" is not /əˈmɛɹəkən/ but /ˈmɚkən/. Apocope example: the Old French word for "state" is "estat," but the "s" has dropped since then, yielding, "état." Syncope example: the final [ə] in Middle English words was pronounced, but was lost, and is only retained in spelling as "silent e."

• Epenthesis: The introduction of a sound between others. Example: in some dialects of English, a [t] is introduced between [n] and [s], like in prince [pɻɪnts].

• Prothesis: The addition of a sound. It differs from liaison in that prothesis always affects a single 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 a syllable because an adjacent syllables is similar or identical. Example: Old English "Anglaland" became Modern English "England", or the common pronunciation of particularly as particuly. This change usually affects commonly used words. The word haplology itself might reduce to *haplogy if it were common enough to be affected by this change.

• Nasalization: Vowels followed by nasal consonants are usually nasalized. If the nasal consonant is lost but the vowel retains its nasalized pronunciation, nasalization has become phonemic, that is, distinctive. Example: French "-in" words used to be pronounced [in], but are now pronounced as [ɛ ̃], and the [n] is no longer pronounced.

Assimilation is a regular and frequent sound change process by which a phoneme changes to match an adjacent phoneme in a word. ... Dissimilation, in the context of phonology, is a phenomenon whereby similar consonant sounds in a word have a tendency to become different over time, so as to ease pronunciation. ... Middle English is the name given by historical linguistics to the diverse forms of the English language spoken between the Norman invasion in 1066 and the mid-to-late 15th century, when the Chancery Standard, a form of London-based English, began to become widespread, a process aided by the... The English language is a West Germanic language that originates in England. ... Metathesis is a sound change that alters the order of phonemes in a word. ... Tonogenesis is the appearance of contrasting tone in a previously non-tonal language, generally as a result of regular phonological changes. ... This article should be translated from material at fr:Liaison. ... In music, see elision (music). ... An apocope or apocopation is a type of metaplasm that refers to a word formed by removing the end of a longer original word. ... Syncope has two distinct and apparantly unrelated meanings, one in linguistics and another in medicne. ... In poetry and phonetics, epenthesis (Greek epi, on × en, in + thesis, putting) is the insertion of a phoneme or syllable into a word, usually to facilitate pronunciation. ... Prothesis is the addition of a sound to a word. ... Haplology is defined as the elimination of a syllable when two consecutive identical or similar syllables occur. ... In phonetics, nasalization is the production of a sound while the velum is lowered, so that air escapes partially or wholly through the nose during the production of the sound. ... In human language, a phoneme is a set of phones (speech sounds or sign elements) that are cognitively equivalent. ...

Examples of specific historical sound changes

• Umlaut
• Grimm's law
• Verner's law
• High German consonant shift
• Anglo-Frisian nasal spirant law