Morphological rules

It is common knowledge that over time words may change both their form and their meaning. Knowing the etymology of a word requires familiarity with the ways in which its phonetic shape has evolved, and familiarity with the evolution of its semantic content. Recognizing the variants of the word components enables us to link words together in more interesting and revealing ways. This and the following two chapters will deal with some regular changes in the phonological form of roots, affixes, and whole words. We will refer to these regularities as morphological rules.

Types of allomorphy

Many of the alternations that we find in roots and affixes can be attributed to the interaction of phonological properties, in which case we talk of regular allomorphy. Regular allomorphs are said to be transparent because one can easily recognize that the two forms are variants of a single form. The changes that the morphemes undergo may affect only the pronunciation of a morpheme, or both its spelling and pronunciation. In either case the variation can be described in terms of regular changes; in that sense, the allomorphs are predictable.

The first type of regularity is illustrated by the pair invent–convene, both derived from the root √ven ‘come, bring.’ More examples of this type of allomorphy are locus–allocate from √loc ‘place,’ dysphagia–necrophagous from √phag ‘eat,’ psychiatry–pediatric from √iatr ‘treat,’ bibliophile–philosophy from √phil ‘love,’ sole–solitude from √sol ‘alone, single.’