Ans. Middle English period is accepted to be from AD 1150-1500. Two significant events distinguish Middle and Modern English. These are (a) the introduction of printing technology and (b) the 'Great Vowel Shift'.
The printing press set up by William Caxton in AD 1476 has played a historic role in the development of English, because it helped to standardize the language. While Middle English was dialectical, Modern English is a standard language, though it also has regional and international varieties.The other major linguistic change in the pronunciation of the English long vowels. The changes began in about AD 1400 and were fully established by the end of the Middle period. These phonological changes are seen as the last barrier between the English of the early times and that of now.