mid vowels. They derived from the Old English diphthongs and . There is no direct evidence that there was ever a distinction between open-mid and close-mid , but it can be assumed because of the corresponding distinction in the unrounded mid front vowels. would have derived directly from Old English , and derived from the open syllable lengthening of short , from the Old English short diphthong . The quality of the short open vowel is unclear. Early in Middle English, it presumably was central since it represented the coalescence of the Old English vowels and , and at the time of Middle English breaking, it could not have been a front vowel since rather than was introduced after it. During the Early Modern English period, it was fronted, in most environments, to in southern England, and it and even closer values are found in the contemporary speech of southern England, North America and the southern hemisphere: it remains in much of Northern England, Scotland and the Caribbean. Meanwhile, the long open vowel, which developed later because of open syllable lengthening, was . It was gradually fronted, to successively , and , in the 16th and the 17th centuries. Diphthongs 1The Old English sequences , produced late Middle English , apparently after passing through early Middle English : OE grōwan ('grow') > LME . However, early Middle English produced by Middle English breaking became late Middle English : OE tōh (tough') > EME > LME . Apparently, early became before the occurrence of Middle English breaking, which generated new occurrences of , which later became . All of the above diphthongs came about within the Middle English era. Old English had a number of diphthongs, but all of them had been reduced to monophthongs in the transition to Middle English. Middle English diphthongs came about by various processes and at various time periods. Diphthongs tended to change their quality over time. The changes above occurred mostly between early and late Middle English. Early Middle English had a distinction between open-mid and close-mid diphthongs, and all of the close-mid diphthongs had been eliminated by late Middle English. The following processes produced the above diphthongs: Reinterpretation of Old English sequences of a vowel followed by , > , or : OE weġ ('way') > EME > LME OE dæġ ('day') > ME Middle English breaking before (, ) Borrowing, especially from Old