morphophonology

Morphophonology is the study of how morphology and phonology interact in the sound structure of languages. It investigates how morphemes—the meaningful units of grammar—are realized phonetically and how phonological processes produce alternate pronunciations (allomorphs) of a morpheme depending on context. The field sits at the interface of morphology and phonology, with attention to patterns of sound change that are conditioned by morphological structure rather than occurring as free variation.

Key concerns include allomorphy and morphophonemic alternations, epenthesis and deletion across morpheme boundaries, assimilation and consonant mutation triggered by affixation, and vowel harmony or ablaut. These processes can occur within a stem or at the boundary between a stem and an affix, shaping the phonological shape of words in systematic ways. Studying morphophonology often involves describing the rules or constraints that determine which phonetic form a morpheme takes in a given environment.

Illustrative English examples include the plural suffix -s, realized as [s], [z], or [ɪz] depending on the final sound of the base (cat→cats [s], dog→dogs [z], bus→buses [ɪz]); and the past tense suffix -ed, pronounced as [t], [d], or [ɪd]. Ablaut patterns in strong verbs (sing-sang-sung) show internal vowel alternations linked to morphological information. Turkish vowel harmony, affecting suffix vowels, is another well-known morphophonological phenomenon. The study of morphophonology thus illuminates how sound and meaning interact across word formation and historical change.