Fusion (phonetics)

In phonetics and historical linguistics, fusion, or coalescence, is a sound change where two or more segments with distinctive features merge into a single segment. This can occur both on consonants and in vowels. A word like educate is one that may exhibit fusion, e.g. /ˈɛdjʊkeɪt/ or /ˈɛdʒʊkeɪt/. A merger between two segments can also occur between word boundaries, an example being the phrase got ya /ˈɡɒt jə/ being pronounced like gotcha /ˈɡɒtʃə/. Most cases of fusion lead to allophonic variation, though some sequences of segments may lead to wholly distinct phonemes.

A common form of fusion is found in the development of nasal vowels, which frequently become phonemic when final nasal consonants are lost from a language. This occurred in French and Portuguese. Compare the French words un vin blanc [œ̃ vɛ̃ blɑ̃] "a white wine" with their English cognates, one, wine, blank, which retain the n's.

Often the resulting sound has the place of articulation of one of the source sounds and the manner of articulation of the other, as in Malay.

Vowel coalescence is extremely common. The resulting vowel is often long, and either between the two original vowels in vowel space, as in [ai] → [eː] → [e] and [au] → [oː] → [o] in French (compare English day [deɪ] and law [lɔː]), in Hindi (with [ɛː], [ɔː]), and in some varieties of Arabic; or combines features of the vowels, as in [ui] → [yː] → [y] and [oi] → [øː] → [ø].

Compensatory lengthening may be considered an extreme form of fusion.