[Page 1631]The term rule-governed alternations is used to describe variations in language based on predictable patterns. This entry describes alternations that occur in adult forms of English and in the speech of children acquiring English. In phonology and morphology, many alternations in pronunciation are associated with particular phonetic conditions. For example, to create a plural noun in English, s is added to the singular form, as in cats (from cat), dogs (from dog), and bees (from bee). This description works for written forms but does not reflect variations in pronunciation. There are, in fact, three pronunciations of the plural: [s], [z], and [əz], determined by the phonetic features of the segment preceding the plural marker:

• (1) When the singular form ends in an affricate /tʃ dʒ/ ...