Allomorph

A particular morpheme is not represented everywhere by the same morph, but by different morphs in different environments. These alternative representation of a morpheme is called allomorphs.

Examples

The plural morpheme in English is regularly represented by the allomorphs [s], [z] and [iz]. The rule is as follows:

(i) kicks [kiks];

(ii) if the morph ends in one of the voiced phonemes (including the vowels), /s/ is represented by [z] (cats [kats]);

(iii) if the morph representing the noun morpheme with which /s/ is combined to form the plural ends with a sibilant ([s], [z] etc.), /s/ is represented by [iz] (sizes [saiziz]).

Other languages

German Allomorphe Chinese 语素变体

Reference

Lyons, John. 1968. Introduction to Theoretical Linguistics. Cambridge: Cambridge University Press.