Sound change

Process of language change that affects pronunciation or sound system structure

Research on sound change is usually conducted under the working assumption that it is regular, which means that it is expected to apply mechanically whenever its structural conditions are met, irrespective of any non-phonological factors like the meaning of the words that are affected. Apparent exceptions to regular change can occur because of dialect borrowing, grammatical analogy, or other causes known and unknown, and some changes are described as "sporadic" and so they affect only one or a few particular words, without any apparent regularity.

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 but are seen as guidelines.

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 an original X.

Sound change is inevitable: All languages vary from place to place and time to time, and neither writing nor media prevents that change.

is to be read, "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":

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

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