Question

Main two reasons to change middle to mordern period of english?

Answer 1

here are both external and internal factors that help explain the change from Old English to Modern English. External factors include who spoke the language and any "political and social factors" that drove change. Internal factors include motivations to structure the language in terms of "punctuation, grammar, vocabulary and written appearance" (Lohr, "From Old English to Modern English").

The period of Old English, also called Anglo-Saxon, dates back to about 450 AD when West German tribes, called the Angles, Saxons, and Jutes, settled in southern Britain. The Germanic language served as the basis for English vocabulary and irregular verbs. Prior to the invasion of the Anglo-Saxons, Rome invaded Britain, starting in 55 BC, leaving significant Latin influence, but that Latin influence was augmented when the Romans introduced Christianity to Britain in the 7th century ("The Romans in Britain"; Lohr). Old English became mostly written in the Latin alphabet with a few Germanic letters included. Viking invasions further influenced Old English vocabulary.  

The period of Modern English begins with the invention of the printing press in the 1400s. The development of printing brought with it a desire to also develop a "standardized variety" of English. William Caxton set up the first prominent printing company in England in 1472, and the books he published helped set a precedent for using the "East Midlands/London variety of English" as the standard form of English (BBC, "William Caxton (c. 1422 - 1492)"; Lohr). Soon, the Johnson's dictionary and grammar books published in the 1700s further helped to codify standard English.