Vowel reduction

A well-researched type of reduction is that of the neutralization of acoustic distinctions in unstressed vowels, which occurs in many languages.[3] 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).Stress-related vowel reduction is a principal factor in the development of Indo-European ablaut, as well as other changes reconstructed by historical linguistics.[4] 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 /s/.Many Germanic languages, in their early stages, reduced the number of vowels that could occur in unstressed syllables, without (or before) clearly showing centralisation.Proto-Germanic and its early descendant Gothic still allowed more or less the full complement of vowels and diphthongs to appear in unstressed syllables, except notably short /e/, which merged with /i/.Vulgar Latin, represented here as the ancestor of the Italo-Western languages, had seven vowels in stressed syllables (/a, ɛ, e, i, ɔ, o, u/).Some Romance languages, like Spanish and Romanian, lack vowel reduction altogether [citation needed].Some regional varieties of the language, influenced by local vernaculars, do not distinguish open and closed e and o even in stressed syllables.Both vowels underwent reduction and were eventually deleted in certain positions in a word in the early Slavic languages, which began in the late dialects of Proto-Slavic.[7] Also in Munster Irish, an unstressed short vowel is not reduced to schwa if the following syllable contains a stressed /iː/ or /uː/: ealaí /aˈl̪ˠiː/ ('art'), bailiú /bˠaˈlʲuː/ ('gather').[8] In Ulster Irish, long vowels in unstressed syllables are shortened but are not reduced to schwa: cailín /ˈkalʲinʲ/ ('girl'), galún /ˈɡalˠunˠ/ ('gallon').
Cardinal vowel chart showing peripheral (white) and central (blue) vowel space, based on the chart in Collins & Mees (2003 :227)
Phonemic mergerphonetic transcriptionsInternational Phonetic AlphabetphoneticsvowelsstresssonoritydurationMuscogee languageAustralian EnglishNear-frontCentralNear-backNear-closeNear-openmid-centralizationunstressed vowelscentralizedclippinglanguage acquisitionNon-native pronunciations of EnglishAnglophone pronunciation of foreign languagessecond languageIndo-European ablauthistorical linguisticsspoken languagewritten counterpartlanguage varietylanguage standardFinnishSpanishsyllable-timed languagesMexican Spanishphonemic (phonological)phonemesProto-GermanicGothicOld High GermanOld SaxonOld NorseOld EnglishStress and vowel reduction in EnglishEnglish languagesyllabic consonantphonologicalOld LatinparticiplesClassical LatinVulgar LatinItalo-Western languagesRomance languagesItalianRomanianregional varietieslocal vernacularsNeapolitanSicilianCatalanValencianvowel harmonyPortuguesePortuguese phonologyEuropean PortugueseBrazilian PortugueseBulgarian Vowel reduction in RussianStandard RussianHavlík's lawProto-SlavicSlavic languagesMunster IrishUlster IrishClipping (phonetics)ElisionSilent letterUnstressed vowelBolinger, DwightTimingSyllableMetrical footTone contourPitch accentRegisterDownstepUpstepDowndriftTone terracingFloating toneTone sandhiTone letterSecondary stressAccentLengthChronemeGeminationVowel lengthExtra-shortnessProsodyIntonationPitch contourPitch resetLoudnessProsodic unit