Phonetic changes are 'regular.' All but one [...] of the particular phonetic laws represented in our tables affect all examples of the sound in question or, if the phonetic change is conditional, all examples of the same sound that are analogously circumstanced.
- Sapir (1921), a pag.180

The second type of change is illustrated in the development of Anglo-Saxon long 'o' to long 'e', via 'ö', under the influence of a following 'i' [...] we may say that [...] the old long 'o' 'split' into two sounds -long 'o', eventually 'u', and long 'e', eventually 'i'.
- Sapir (1921), a pag.180