In phonetics, an allophone is one of several similar phones that belong to the same phoneme. A phone is a sound that has a definite shape as a sound wave, while a phoneme is a basic group of sounds that can distinguish words (i.e. changing one phoneme in a word can produce another word); speakers of a particular language perceive a phoneme as a single distinctive sound in that language. Thus an allophone is a phone considered as a member of one phoneme.

We may distinguish complementary allophones, which are distributed regularly within the idiolect of the same speaker according to phonetic environment, from free variants, which are a matter of personal habit or regional accent.

In the case of complementary allophones, each allophone is used in a specific phonetic context and many times there is some sort of phonological process. Not all phonemes have significantly different allophones, but there are always minor differences in articulation from one piece of speech to the next.