• English Language
• History of the English Language: A Mini-Anthology
• Key Events in the History of the English Language
• Modern English
• Old English
• Spoken English
• Written English

Examples and Observations:

• Chaucer's Canterbury Tales
  "Whan that Aprill, with his shoures soote
  The droghte of March hath perced to the roote
  And bathed every veyne in swich licour,
  Of which vertu engendred is the flour . . .."
  ["When the sweet showers of April have pierced
  The drought of March, and pierced it to the root
  And every vein is bathed in that moisture
  Whose quickening force will engender the flower . . .."]
  (Geoffrey Chaucer, General Prologue to The Canterbury Tales, late 14th century. Translation by David Wright. Oxford Univ. Press, 2008)
• French Influence on Middle English
  "From 1150 to 1500 the language is known as Middle English. During this period the inflections, which had begun to break down during the end of the Old English period, become greatly reduced. . . .
  
  "By making English the language mainly of uneducated people, the Norman Conquest [in 1066] made it easier for grammatical changes to go forward unchecked.
  
  "French influence is much more direct and observable upon the vocabulary. Where two languages exist side by side for a long time and the relations between the people speaking them are as intimate as they were in England, a considerable transference of words from one language to the other is inevitable. . . .
  
  "When we study the French words appearing in English before 1250, roughly 900 in number, we find that many of them were such as the lower classes would become familiar with through contact with a French-speaking nobility: (baron, noble, dame, servant, messenger, feast, minstrel, juggler, largess). . . . In the period after 1250, . . . the upper classes carried over into English an astonishing number of common French words. In changing from French to English, they transferred much of their governmental and administrative vocabulary, their ecclesiastical, legal, and military terms, their familiar words of fashion, food, and social life, the vocabulary of art, learning, and medicine."
  (A. C. Baugh and T. Cable, A History of the English Language. Prentice-Hall, 1978)

• "[T]he transition from Middle to early modern English is above all the period of the elaboration of the English language. Between the late 14th and 16th centuries, the English language began increasingly to take on more functions. These changes in function had, it is argued here, a major effect on the form of English: so major, indeed, that the old distinction between 'Middle' and 'modern' retains considerable validity, although the boundary between these two linguistic epochs was obviously a fuzzy one."
  (Jeremy J. Smith, "From Middle to Early Modern English." The Oxford History of English, ed. by Lynda Mugglestone. Oxford Univ. Press, 2006)
• Chaucer on Changes in the "Forme of Speeche"
  "Ye knowe ek that in forme of speeche is chaunge
  Withinne a thousand yeer, and wordes tho
  That hadden pris, now wonder nyce and straunge
  Us thinketh hem, and yet thei spake hem so,
  And spedde as wel in love as men now do;
  Ek for to wynnen love in sondry ages,
  In sondry londes, sondry ben usages."
  ["You know also that in (the) form of speech (there) is change
  Within a thousand years, and words then
  That had value, now wonderfully curious and strange
  (To) us they seem, and yet they spoke them so,
  And succeeded as well in love as men now do;
  Also to win love in sundry ages,
  In sundry lands, (there) are many usages."]
  (Geoffrey Chaucer, Troilus and Criseyde, late 14th century. Translation by Roger Lass in "Phonology and Morphology." A History of the English Language, edited by Richard M. Hogg and David Denison. Cambridge Univ. Press, 2008)