APA Dictionary of Psychology

n. in linguistics, any of several different speech sounds or written forms that are used to represent the same morpheme. For example, the [s] sound at the end of cats and the [z] sound at the end of dogs represent the same noun-plural morpheme and are therefore allomorphs. Similarly, in writing, the -t at the end of burnt and the -ed at the end of turned are allomorphs representing the same past-tense morpheme. —allomorphic adj.