Reduced vowel

In phonetics, vowel reduction is any of various changes in the acoustic quality of vowels, which are related to changes in stress, sonority, duration, loudness, articulation, or position in the word (e.g. for Creek language), and which are perceived as "weakening". It most often makes the vowels shorter as well.

Such a vowel may be called reduced or weak. An unreduced vowel may be contrasted as full or strong.

Phonetic reduction most often involves a centralization of the vowel, that is, a reduction in the amount of movement of the tongue in pronouncing the vowel, as with the characteristic change of many unstressed vowels at the ends of English words to something approaching schwa. A well-researched type of reduction is that of the neutralization of acoustic distinctions in unstressed vowels, which occurs in many languages. The most common reduced vowel is schwa.

Whereas full vowels are distinguished by height, backness, and roundness, according to Bolinger (1986), reduced unstressed vowels are largely unconcerned with height or roundness. English /ə/, for example, may range phonetically from mid [ə] to [ɐ] to open [a]; English /ɨ/ ranges from close [i], [ɪ], [e], to open-mid [ɛ]. The primary distinction is that /ɨ/ is further front than /ə/, contrasted in the numerous English words ending in unstressed -ia. That is, the jaw, which to a large extent controls vowel height, tends to be relaxed when pronouncing reduced vowels. Similarly, English /ɵ/ ranges through [ʊ] and [o]; although it may be labialized to varying degrees, the lips are relaxed in comparison to /uː/, /oʊ/, or /ɔː/. The primary distinction in words like folio is again one of backness. However, the backness distinction is not as great as that of full vowels; reduced vowels are also centralized, and are sometimes referred to by that term. They may also be called obscure, as there is no one-to-one correspondence between full and reduced vowels.

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