biuniqueness (n.)

A principle in some approaches to PHONOLOGY which states that any sequence of PHONEMES will be represented by a unique sequence of PHONES, and vice versa – in other words, there is a one-to-one (or ‘reversible’) correspondence between phones and phonemes in each utterance. For example, in the word bin, the relationship between the two LEVELS of analysis can be shown as

There are, however, several cases where this straightforward correlation does not apply, and where the notion of a phoneme as a unique class of sounds consequently is invalid. In such cases, one phone is assigned to more than one phoneme, depending on the CONTEXT. The biuniqueness condition, along with the conditions of LINEARITY and INVARIANCE, on which it depends, was particularly criticized by GENERATIVE phonologists, as part of their general attack on TAXONOMIC phonemics.