Morphology and Phonology

Abstract This entry provides an overview of the fields of morphology and phonology and examines how these interact with particular attention to implications for first and second language acquisition. Morphology is described as the system governing word formation and grammatical structure, while phonology concerns the organization and patterning of speech sounds. We describe how these two domains interact in systematic sound alternations conditioned by morphological structure and phonological environments, a set of phenomena collectively referred to as morphophonology. Using cross‐linguistic examples, we illustrate core morphophonological processes such as phonotactics, prosody, lexical morphology, and orthography, as well as common types of sound change resulting from assimilation, syllable structure preservation, and dissimilation. We also review key debates regarding whether morphophonological variation reflects underlying linguistic competence or performance‐based constraints. We synthesize research on the acquisition of morphophonological structures in both first and second languages, highlighting the role of phonological awareness, prosodic transfer, and cross‐linguistic influence. Special attention is given to the Prosodic Transfer Hypothesis as an explanatory framework for variable learner production. The chapter concludes by identifying gaps in current research and outlining directions for future work, particularly with adult and plurilingual learners and in under‐represented language contexts.