APA Dictionary of Psychology

n. in linguistics, any of several slightly different speech sounds that are regarded as contextual variants of the same phoneme. For example, in English the aspirated [p] sound at the beginning of paid and the unaspirated [p] sound in spade have no contrastive function in the phonological system of the language and are therefore regarded as allophones of the same phoneme, /p/. —allophonic adj.