Allomorphy

Allomorphy is a phenomenon in morphology whereby a single morpheme has multiple phonological realizations, called allomorphs. The choice among allomorphs is conditioned by the linguistic context rather than by changes in meaning or grammatical function. Allomorphs are surface forms of the same abstract unit; they reflect predictable phonological adjustments or irregular lexical patterns. When the variation follows regular rules, it is called regular allomorphy; irregular or lexicalized patterns are often described as suppletion or irregular alternations.

A classic example is the English plural morpheme, realized as one of three allomorphs: [s], [z], or [ɪz], depending on the final sound of the stem. Thus cat(s) ends with [s], dog(s) with [z], and bus(es) with [ɪz]. Another well-known case is the past tense marker -ed, which is pronounced as [t], [d], or [ɪd] in walked, grabbed, and wanted, respectively.

Zero allomorphy also occurs, where the morphophonological realization is null. For some nouns, the plural morpheme is not overtly realized in the surface form (e.g., sheep, deer in standard usage), even though a plural meaning is present.

Turkish provides a cross-linguistic example of allomorphy conditioned by vowel harmony: the plural suffix appears as -lar or -ler, chosen to agree with the stem vowel’s backness.

Distinctions are sometimes drawn between allomorphy and suppletion: allomorphy involves phonologically related realizations of the same morpheme, while suppletion involves forms that are phonologically unrelated. Allomorphy is a widespread phenomenon across languages, shaping how grammatical meaning is expressed in sound.