Content. Introduction chapter. I. The Middle English and the Modern English Periods

CHAPTER.II. EVOLUTION OF THE GRAMMATICAL SYSTEM FROM THE
11TH TO 18TH C.
2.1. Evolution of the Sound System from the 11^th to the 18^th centuries
The sound system of the English language has undergone profound changes in the thousand years which have elapsed since the Old English period. The changes affected the pronunciation of words, word stress, and the system of vowel and consonant phonemes. The change of the sound system can be grouped into two main stages:

• 
  Early Middle English changes, which show the transition from Written Old English to Late Middle English – the age of literary flourishing or "the age of Chaucer";
  
• 
  Early New English changes, which show the transition from Middle English to later New English – the language of the 18^th and the 19^th centuries.
  

One of the most important of them was the Great Vowel Shift. Early Middle English witnessed the greatest event in the history of English vowels - the Great Vowel Shift – which involved the change of all Middle English long monophthongs, and probably some of the diphthongs. The Great Vowel Shift is the name given to a series of changes of long vowels between the 14^th and the18th centuries. During this period all the long vowels became closer or were diphthongised. The changes can be defined as "independent".
As they were not caused by any apparent phonetic conditions in the syllable or in the word, but they affected regularly every stressed long vowel in any position. As the spelling had been already stabilized the Great Vowel Shift was not reflected in it. As a result the meaning of the letters and digraphs designating long vowels has changed radically. The separate stages of the changes in the system of long vowels in the process of the Great Vowel Shift can be shown as following:
a: > ei; : > e: > i:; i: > ai; : > ou; o: > u:; u: . au.
If we compare the system of long vowels of the pre-Great Vowel Shift period with the system of the post Great Vowel Shift period, we have to state that there appeared no new vowels, that is the Great Vowel Shift did not result in any new vowels. So we should rather speak of rearrangement of long vowels: