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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〔 (Acoustic vowel reduction in Creek: Effects of distinctive length and position in the word ) (pdf)〕), 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''. ==Weakening of vowel articulation== 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 (1989), reduced unstressed vowels are largely unconcerned with height or roundness. English , for example, may range phonetically from mid to to open ; English ranges from close , , , to open-mid . The primary distinction is that is further front than , 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 ranges through and ; although it may be labialized to varying degrees, the lips are relaxed in comparison to , , or . 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. (Bolinger 1989:347) Sound duration is a common factor in reduction: In fast speech, vowels are reduced due to physical limitations of the articulatory organs, e.g., the tongue cannot move to a prototypical position fast or completely enough to produce a full-quality vowel (compare with clipping). Different languages have different types of vowel reduction, and this is one of the difficulties in language acquisition; see, e.g., "Non-native pronunciations of English" and "Anglophone pronunciation of foreign languages". Vowel reduction of second language speakers is a separate study. Stress-related vowel reduction is a principal factor in the development of Indo-European ablaut, as well as other changes reconstructed by historical linguistics. There are several ways to distinguish full and reduced vowels in transcription. Some English dictionaries mark full vowels for secondary stress, so that e.g. is a full unstressed while is a reduced unstressed ''schwi''. The vowel quality may be considered distinct, with reduced vowels centralized, e.g. with full vs reduced . Some transcriptions of English and Russian use non-IPA letters for reduced vowels, such as and in English or and for unstressed and in Russian. Such vowel reduction is one of the sources of distinction between a spoken language and its written counterpart. Vernacular and formal speech often have different levels of vowel reduction, and so the term "vowel reduction" is also applied to differences in a language variety with respect to, e.g., the language standard. Some languages, such as Finnish, Hindi, and classical Spanish, are claimed to lack vowel reduction. Such languages are often called syllable-timed languages.〔R. M. Dauer. "Stress-timing and syllable-timing reanalysed". Journal of Phonetics. 11:51–62 (1983).〕 At the other end of the spectrum, Mexican Spanish is characterized by the reduction or loss of the unstressed vowels, mainly when they are in contact with the sound .〔Eleanor Greet Cotton, John M. Sharp (1988) ''Spanish in the Americas, Volumen 2'', pp.154–155, (URL )〕〔Lope Blanch, Juan M. (1972) ''En torno a las vocales caedizas del español mexicano'', pp. 53–73, Estudios sobre el español de México, editorial Universidad Nacional Autónoma de México, México (URL ).〕 It can be the case that the words ''pesos'', ''pesas'', and ''peces'' are pronounced the same: . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「vowel reduction」の詳細全文を読む スポンサード リンク
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