2. Explaining sound change
When specific languages are thought to be genetically related, because of systematic and recurrent form-meaning similarities in a large number of lexical roots in particular involving basic vocabulary as well as grammatical morphemes, it is usually possible to set up regular sound correspondences between segments in cognate forms. Moreover, as illustrated in the preceding chapter, specific sound changes may be reconstructed as a next step. Experience has shown not only that similar principles of regular sound change apply to language after language, but also that similar types of sound changes occur again and again in different parts of the world. Some of these more widespread structural changes in sound systems are illustrated next.