Editing Sound change (section)

==Formal notation==
{{See also|Phonological rule}}
A statement of the form

::{{code|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 language|Proto-Oceanic]] (POc.) *t is reflected as {{IPA|[f]}} in [[Rotuman language|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: *{{IPA|[t]}} first changed to {{IPA|[θ]}} (like the initial consonant of [[English language|English]] ''thin''), which has since yielded {{IPA|[f]}} and can be represented more fully:

:: t > {{IPA|θ}} > 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 language|Italian]]" (such as in ''caballum, dēbet'' > ''cavallo'' 'horse', ''deve'' 'owe (3rd pers. sing.)'

Here is a second example:

::PIr. [&minus;cont][&minus;voi] > [+cont] /__[C][+cont]

:= "A preconsonantal voiceless non-continuant (voiceless stop) changed into corresponding a voiceless continuant ([[fricative consonant|fricative]]) in [[Proto-Iranian]] (PIr.)" when it was immediately followed by a continuant consonant (a [[resonant consonant|resonant]] or a fricative): [[Proto-Indo-Iranian]] *''pra'' 'forth' > [[Avestan language|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 languages|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 language|Greek]] (''Gk.'')".

That can be simplified to

::Gk. P > ∅ / __#

in which P stands for any [[plosive consonant|plosive]].