Edward Sapir (1884–1939). Language: An Introduction to the Study of Speech. 1921.
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what is probably the most central problem in linguistic history, gradual phonetic change. “Phonetic laws” make up a large and fundamental share of the subject-matter of linguistics. Their influence reaches far beyond the proper sphere of phonetics and invades that of morphology, as we shall see. A drift that begins as a slight phonetic readjustment or unsettlement may in the course of millennia bring about the most profound structural changes. The mere fact, for instance, that there is a growing tendency to throw the stress automatically on the first syllable of a word may eventually change the fundamental type of the language, reducing its final syllables to zero and driving it to the use of more and more analytical or symbolic5 methods. The English phonetic laws involved in the rise of the words foot, feet, mouse and mice from their early West-Germanic prototypes fot, foti, mus, musi6 may be briefly summarized as follows:
1. In foti “feet” the long o was colored by the following i to long ö, that is, o kept its lip-rounded quality and its middle height of tongue position but anticipated the front tongue position of the i; ö is the resulting compromise. This assimilatory change was regular, i.e., every accented long o followed by an i in the following syllable automatically developed to long ö; hence tothi “teeth” became töthi, fodian “to feed” became födian. At first there is no doubt the alternation between o and ö was not felt as intrinsically significant. It could only have been an unconscious mechanical adjustment such as may be observed in the speech of many to-day who modify the “oo” sound of words like you and few in the
