| a series of changes in the quality of the long vowels between Middle and Modern English as a result of which all were raised, while the high vowels (ē) and (o̅o̅), already at the upper limit, underwent breaking to become the diphthongs (ī) and (ou). |
| Great Vowel Shift n. A series of phonetic changes occurring in Early Modern English in which the Middle English low and mid long vowels were raised, (ä) and (ō) becoming (ā) and (ōō), for example, while the high long vowels (ē) and (ōō) became the diphthongs (ī) and (ou). |