Morphological rules

Etymology is the study of the history of words. 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. 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

We can divide all the roots and affixes of English into three types of allomorphy:

1. (1) Unchanging – i.e., zero allomorphy.

2. (2) Irregular allomorphy: these are morphemes whose variant forms are not derived from one another by regular rules. These unpredictable allomorphs are said to be opaque because the relationship between them, though historically valid, is not apparent to the ordinary speaker of the language.

3. (3) Regular allomorphy: these are morphemes whose variation can be described in terms of regular rules; the allomorphs are predictable. Such allomorphs are said to be transparent because one can easily recognize that the two forms are variants of a single form.

Zero allomorphy

Morphemes belonging to this group preserve their base form in all the derivatives where they appear. Thus in the family of the root √phil “love,” this morpheme remains unchanged in Philadelphia, philanthropy, philology, philosophy, zoophilia.