Allomorph

In linguistics, an allomorph is a variant phonetic form of a morpheme, or in other words, a unit of meaning that varies in sound and spelling without changing the meaning. The term allomorph describes the realization of phonological variations for a specific morpheme. The different allomorphs that a morpheme can become are governed by morphophonemic rules. These phonological rules determine what phonetic form, or specific pronunciation, a morpheme will take based on the phonological or morphological context in which it appears.

Allomorphy in English involves the variation of morphemes in their phonetic form based on specific linguistic contexts, a phenomenon governed by morphophonemic rules. For instance, the past tense morpheme "-ed" can manifest in different forms—[-əd], [-t], or [-d]—depending on the final sound of the verb stem. This variability is not random but follows predictable patterns, such as the insertion of a schwa [ə] or assimilation to the voicing of the preceding consonant. Similarly, English plural morphemes exhibit three allomorphs: [-s], [-z], and [-əz], with pronunciation determined by the final sound of the noun, whether it be a voiceless consonant, a voiced consonant, or a sibilant. In addition, negative prefixes like "in-" display allomorphy, changing from [ɪn-] to [ɪŋ-] or [ɪm-] depending on the following consonant's place of articulation. This systematic variation reflects the intricate relationship between phonology and morphology in language, with allomorph selection being guided by both phonological environment and morphological constraints (Pak, 2016; Stanton, 2022).