Middle English and Early New English vowel system.

In Early ME the pronunciation of unstressed syllables became increasingly indistinct. As compared to OE, which distinguishes five short vowels in unstressed position [e/i], [a] and [o/u], Late ME had only two vowels in unaccented syllables: [ə] and [i], e.g. ME tale [΄ta:lə] – NE tale, ME body [΄bodi] – NE body. The final [ə] disappeared in Late ME though it continued to be spelt as -e. When the ending –e survived only in spelling, e.g. ME stone, rode [´stone], [´rode] – NE stone, rode. The shifting of word stress in ME and NE, vocalization of [r] in such endings as writer, actor, where [er] and [or] became [ə]. Quantitative vowel changes in Early ME In Early ME vowel length began to depend on phonetic conditions. The earliest of positional quantitative changes was the readjustment of quantity before some consonant clusters: 1) Short vowels were lengthened before two consonants – a sonorant and a plosive; consequently, all vowels occurring in this position remained or became long, e.g. ME wild [wi:ld] – NE wild. 2) All other groups of two or more consonants produced the reverse effect: they made the preceding long vowels short, and all vowels in this position became or remained short, e.g. ME kepte [΄keptə] – NE kept. 3) Short vowels became long in open syllables, e.g. ME name [na:mə] – NE name. Qualitative vowel changes. Development of monophthongs [y] and [y:] disappeared in Early ME, merging with various sounds in different dialectal areas. In Early ME the dialectal differences grew. In Early ME the long OE [a:] was narrowed to [o:]. This was and early instance of the growing tendency of all long monophthongs to become closer, so [a:] became [o:] in all the dialects except the Northern group, e.g. OE stān – ME (Northern) stan(e), (other dialects) stoon, stone – NE stone. The short OE [æ] was replaced in ME by the back vowel [a], e.g. OE þǽt > ME that [Өat] > NE that. Development of diphthongs In Early ME the diphthongs were contracted to monophthongs: the long [ea:] coalesced (united) with the reflex of OE [ǽ:] – ME [ε:]; the short [ea] ceased to be distinguished from OE [æ] and became [a] in ME; the diphthongs [eo:], [eo] – as well as their dialectal variants [io:], [io] – fell together with the monophthongs [e:], [e], [i:], [i]. As a result of these changes the vowel system lost two sets of diphthongs, long and short. In Early ME the sounds [j] and [γ] between and after vowels changed into [i] and [u] and formed diphthongs together with the preceding vowels, e.g. ME day [dai]. These changes gave rise to two sets of diphthongs: with i-glides and u-glides. The same types of diphthongs appeared also from other sources: the glide -u developed from OE [w] as in OE snāw, which became ME snow [snou], and before [x] and [l] as in Late ME smaul and taughte.