allomorphe

An allomorph is one of the phonological variants of a morpheme, the smallest unit of meaning in a language. The same morpheme can surface in different sounds or shapes depending on phonological context, without changing its meaning. Allomorphs belong to the same underlying morpheme and share the same semantic content, even though their pronunciation differs.

A common example is the English plural suffix -s, which has three allomorphs: [s], [z], and [ɪz]. For example, cats is pronounced with [s], dogs with [z], and buses with [ɪz]. Another well-known case is the past tense suffix -ed, which surfaces as [t] after voiceless endings, [d] after voiced endings, and [ɪd] after t or d sounds, as in walked, robbed, and wanted. These forms illustrate how allomorphy is conditioned by the phonological environment surrounding the morpheme.

Allomorphy can be described in terms of conditioning environments, often in complementary distribution, where each allomorph appears in a distinct context. The same underlying morpheme thus yields different realizations depending on adjacent sounds, voicing, or other phonological factors. In some languages, more complex morphophonemic rules govern allomorph selection, while in others, a simpler set of conditioned variants suffices.

An important distinction is between allomorphy and spelling. The written form of a word may not reveal its phonological allomorphs; orthography can be invariant while pronunciation varies. Additionally, some irregular forms, such as suppletion (for example was/were), are not considered true allomorphs of the same morpheme, representing a separate type of morphological irregularity.