Allophon

Allophon, often written allophone in English, is a term in phonology that designates a variant pronunciation of a phoneme in a particular phonetic context. The phoneme is the abstract unit, while the allophone is one of its possible surface realizations. Different allophones of the same phoneme do not distinguish meaning in the language; they are interchangeable in the sense that they do not create a minimal pair.

In describing allophony, two main patterns are recognized. Complementary distribution occurs when each allophone appears in a distinct, non-overlapping environment, such as after certain consonants or within certain syllable positions. Free variation occurs when more than one allophone can occur in the same environment without changing meaning, and the choice is not phonologically determined.

Common examples are often used to illustrate allophony in English. The initial /p/ has two well-known allophones: an aspirated [pʰ] as in pin, and an unaspirated [p] as in spin. The American English flap [ɾ] can be an allophone of /t/ or /d/ between vowels when the second vowel is unstressed, as in water. The lateral /l/ also shows allophony: a light [l] typically occurs before vowels, while a dark [ɫ] occurs in syllable-coda position, as in leaf versus ball.

Allophony is language-specific and is described by phonological rules or representations that capture when and how these surface realizations occur.