Sound change

Formal notation

A statement of the form

A > B

is to be read as "Sound A changes into (or is replaced by, is reflected as, etc.) sound B". Therefore, A belongs to an older stage of the language in question, and B belongs to a more recent stage. The symbol ">" can be reversed, B < A, which also means that the (more recent) B derives from the (older) A":

POc. *t > Rot. f

means that "Proto-Oceanic (POc.) *t is reflected as in Rotuman (Rot.)".

The two sides of such a statement indicate only the start and the end of the change, but additional intermediate stages may have occurred. The example above is actually a compressed account of a sequence of changes: * first changed to (like the initial consonant of English thin), which has since yielded and can be represented more fully:

t > > f

Unless a change operates unconditionally (in all environments), the context in which it applies must be specified:

A > B /X__Y

= "A changes to B when it is preceded by X and followed by Y."

For example:

It. b > v /[vowel]__[vowel], which can be simplified to just

It. b > v /V__V (in which the V stands for any vowel)

= "Intervocalic [b] (inherited from Latin) became [v] in Italian" (such as in caballum, dēbet > cavallo 'horse', deve 'owe (3rd pers. sing.)'

Here is a second example:

PIr. [−cont][−voi] > [+cont] /__[C][+cont]

= "A preconsonantal voiceless non-continuant (voiceless stop) changed into a corresponding voiceless continuant (fricative) in Proto-Iranian (PIr.) when it was immediately followed by a continuant consonant (a resonant or a fricative)": Proto-Indo-Iranian *pra 'forth' > Avestan fra; *trayas "three" (masc. nom. pl.)> Av. θrayō; *čatwāras "four" (masc. nom. pl.) > Av. čaθwārō; *pśaws "of a cow" (nom. *paśu) > Av. fšāoš (nom. pasu). The fricativization did not occur before stops and so *sapta "seven" > Av. hapta. (However, in the variety of Iranian that led to Old Persian, fricativization occurred in all clusters: Old Persian hafta "seven".)

The symbol "#" stands for a word boundary (initial or final) and so the notation "/__#" means "word-finally", and "/#__" means "word-initially":

Gk. [stop] > ∅ /__#

= "Word-final stops were deleted in Greek (Gk.)".

That can be simplified to

Gk. P > ∅ / __#

in which P stands for any plosive.

Terms for changes in pronunciation

In historical linguistics, a number of traditional terms designate types of phonetic change, either by nature or result. A number of such types are often (or usually) sporadic, that is, more or less accidents that happen to a specific form. Others affect a whole phonological system. Sound changes that affect a whole phonological system are also classified according to how they affect the overall shape of the system; see phonological change.

• Assimilation: One sound becomes more like another, or (much more rarely) two sounds become more like each other. Example: in Latin the prefix *kom- becomes con- before an apical stop () or : contactus' "touched", condere "to found, establish", connūbium "legal marriage". The great majority of assimilations take place between contiguous segments, and the great majority involve the earlier sound becoming more like the later one (e.g. in connūbium, m- + n becomes -nn- rather than -mm-). Assimilation between contiguous segments are (diachronically speaking) exceptionless sound laws rather than sporadic, isolated changes.
• Dissimilation: The opposite of assimilation. One sound becomes less like another, or (much more rarely) two sounds become less like each other. Examples: Classical Latin quīnque "five" > Vulgar Latin *kinkʷe (whence French cinq, Italian cinque, etc.); Old Spanish omne "man" > Spanish hombre. The great majority of dissimilations involve segments that are not contiguous, but, as with assimilations, the great majority involve an earlier sound changing with reference to a later one. Dissimilation is usually a sporadic phenomenon, but Grassmann's Law (in Sanskrit and Greek) exemplifies a systematic dissimilation. If the change of a sequence of fricatives such that one becomes a stop is dissimilation, then such changes as Proto-Germanic *hs to (spelled x) in English would count as a regular sound law: PGmc. *sehs "six" > Old English siex, etc.
• Metathesis: Two sounds switch places. Example: Old English thridda became Middle English third. Most such changes are sporadic, but occasionally a sound law is involved, as Romance *tl > Spanish ld, thus *kapitlu, *titlu "chapter (of a cathedral)", "tittle" > Spanish cabildo, tilde. Metathesis can take place between non-contiguous segments, as Greek amélgō "I milk" > Modern Greek armégō.
• Lenition: "Weakening" of a consonant from one that takes more effort to pronounce (and more constriction in the vocal tract) to one that takes less, e.g. a stop consonant becoming an affricate or fricative.
• Fortition: the opposite of lenition, "strengthening" a consonant, e.g. an approximant becoming an affricate or fricative.
• Reduction: Whereas the weakening of consonants is called lenition, the weakening of vowels is called reduction. For example, in most varieties of English, unstressed vowels often reduce to a schwa, such as the two a's in arena.
• Tonogenesis: Syllables come to have distinctive pitch contours.
• Sandhi: Conditioned changes that take place at word-boundaries but not elsewhere. It can be morpheme-specific, as in the loss of the vowel in the enclitic forms of English is , with subsequent change of to adjacent to a voiceless consonant Frank's not here . Or a small class of elements, such as the assimilation of the of English the, this and that to a preceding (including the of and when the is elided) or : all the often , in the often , and so on. As in these examples, such features are rarely indicated in standard orthography. In a striking exception, Sanskrit orthography reflects a wide variety of such features; thus, tat "that" is written tat, tac, taj, tad,or tan depending on what the first sound of the next word is. These are all assimilations, but medial sequences do not assimilate the same way.
• Haplology: The loss of a syllable when an adjacent syllable is similar or (rarely) identical. Example: Old English Englaland became Modern English England, or the common pronunciation of probably as . This change usually affects commonly used words. The word haplology itself is sometimes jokingly pronounced haplogy.
• Elision, aphaeresis, syncope, and apocope: All are losses of sounds. Elision is the loss of unstressed sounds, aphaeresis the loss of initial sounds, syncope is the loss of medial sounds, and apocope is the loss of final sounds.
  • Elision examples: in the southeastern United States, unstressed schwas tend to drop, so "American" is not but . Standard English is possum < opossum.
  • Syncope examples: the Old French word for "state" is estat, but the s disappeared, yielding état. Similarly, the loss of in English soften, hasten, castle, etc.
  • Apocope examples: the final -e in Middle English words was pronounced, but is only retained in spelling as a silent E. In English and were apocopated in final position after nasals: lamb, long .
• Epenthesis (also known as anaptyxis): The introduction of a sound between two adjacent sounds. Examples: Latin humilis > English humble; in Slavic an -l- intrudes between a labial and a following yod, as *zemya "land" > Russian zemlya (земля). Most commonly, epenthesis is in the nature of a "transitional" consonant, but vowels may be epenthetic: non-standard English film in two syllables, athlete in three. Epenthesis can be regular, as when the Indo-European "tool" suffix *-tlom everywhere becomes Latin -culum (so speculum "mirror" < *speḱtlom, pōculum "drinking cup" < *poH₃-tlom). Some scholars reserve the term epenthesis for "intrusive" vowels and use excrescence for intrusive consonants.
• Prothesis: The addition of a sound at the beginning of a word. Example: word-initial + stop clusters in Latin gained a preceding in Old Spanish and Old French; hence, the Spanish word for "state" is estado, deriving from Latin status.
• Nasalization: Vowels followed by nasal consonants can become nasalized. If the nasal consonant is lost but the vowel retains its nasalized pronunciation, nasalization becomes phonemic, that is, distinctive. Example: French "-in" words used to be pronounced , but are now pronounced , and the is no longer pronounced (except in cases of liaison).

Examples of specific sound changes in various languages

• Anglo-Frisian nasal spirant law
• Canaanite shift
• Cot-caught merger
• Dahl's law
• Grassmann's law
• Great Vowel Shift (English)
• Grimm's law
• High German consonant shift
• Kluge's law
• Onbin
• Phonetic change "f → h" in Spanish
• Ruki sound law
• Slavic palatalization
• Umlaut
• Verner's law