Phonological Constraints and Conditioning in Diachronic Morphology

This chapter offers an overview of ways in which phonological properties or processes may constrain, condition, or shape diachronic patterns in morphology. Phonological factors that can impact morphological change include syllabic and prosodic considerations, segmental phonotactics, and phonological similarity. Other morphological phenomena whose development is influenced by phonological form include contrast preservation and homophony avoidance. Across all types of factors, we find that phonological properties can facilitate, inhibit, or otherwise affect a diversity of morphological change types, including the development of suppletive allomorphy, syncretism, changes to the forms of morphemes, or replacement of one morphological strategy by another. We begin with the observation that accidental sound changes may cause morphological changes, ranging from the simplest case of changes in the form of a morpheme to the more extreme case of exponent loss leading to the reconfiguration of an entire morphological system. In this vein but somewhat different are cases where patterns of morphological change seem to be shaped by phonological well‐formedness considerations, whether these are grammatical or emergent. Contrasting with these types of purely phonological pressures are those that can be characterized as morphological pressures on the phonological forms of morphemes. A number of phenomena can be characterized as appearing to avoid similarity between morphemes or word forms. The conceptual division between phonological drivers and morphological motivations brings us to phenomena that combine both: namely, conditions on paradigm well‐formedness that are sensitive to phonology, and shape diachronic change accordingly. We review evidence for phonological factors in determining the course of analogical leveling, as well as the role of phonological similarity within paradigms in ways that go beyond simple morpheme identity. We conclude with some general remarks on the role of phonology in diachronic morphology.