Mamun -university roman -german philology english department

Chapter 1. GENERAL INFORMATION ABOUT MONOPHTHONG AND DIPTHON.
I.1 Historical background monophthong and dipthong
English  dipthong have undergone many changes since the Old and Middle English periods. The sound changes discussed here involved at least one phoneme which historically was a diphthong. Further information:  Old English  and  Phonogical history of Old English
Old English diphtongs could be short or long . Both kinds arose from sound occurring in Old English itself, although the long forms sometimes also developed from Proto-Germanic diphthongs. They were mostly of the height-harmonic type (both elements at the same height) with the second element further back than the first. The set of diphthongs that occurred depended on dialect (and their exact pronunciation is in any case uncertain). Typical diphthongs are considered to have been as follows:

• 
  high, fully backing, /iu/ /iːu/, spelt ⟨io⟩ (found in Anglian dialects, but merged into /eo/ /eːo/ in Late West Saxon)
  
• 
  high, narrower, possibly /iy/ /iːy/ or /ie/ /iːe/, spelt ⟨ie⟩ (found in Late West Saxon)
  
• 
  mid, /eo/ /eːo/, spelt ⟨eo⟩
  
• 
  low, /æɑ/ /æːɑ/, spelt ⟨ea⟩
  

As with monophthongs, the length of the diphthongs was not indicated in spelling, but in modern editions of OE texts the long forms are often written with a macron: ⟨īo⟩, ⟨īe⟩, ⟨ēo⟩, ⟨ēa⟩.
In the transition from Old to Middle English, all of these diphthongs generally merged with monophthongs.
Middle English phonology is necessarily somewhat speculative, since it is preserved only as a written language. Nevertheless, there is a very large text corpus of Middle English. The dialects of Middle English vary greatly over both time and place, and in contrast with Old English and Modern English, spelling was usually phonetic rather than conventional. Words were generally spelled according to how they sounded to the person writing a text, rather than according to a formalised system that might not accurately represent the way the writer's dialect was pronounced, as Modern English is today.
The Middle English speech of the city of London in the late 14th century (essentially, the speech of Geoffrey Chaucer) is used as the standard Middle English dialect in teaching and when specifying "the" grammar or phonology of Middle English. It is this form that is described below, unless otherwise indicated.
Although the Old English diphthongs merged into monophthongs, Middle English began to develop a new set of diphthongs, in which the second element was a high [i] or [u]. Many of these came about through vocalization of the palatal approximant /j/ or the labio-velar approximant /w/ (which was sometimes from an earlier voiced velar fricative [ɣ], an allophone of /ɡ/), when they followed a vowel. For example:

• 
  OE dæg ("day") and weg ("way") (where the /ɡ/ had been palatalized to /j/) became [dai] and [wɛi]
  
• 
  OE clawu ("claw") and lagu ("law") became [klau] and [lau]
  

Diphthongs also arose as a result of vowel breaking before /h/ (which had allophones [x] and [ç] in this position – for the subsequent disappearance of these sounds, see h-loss). For example:

• 
  OE streht ("straight") became [strɛiçt]
  
• 
  OE þoht ("thought") became [θɔuxt]
  

The diphthongs that developed by these processes also came to be used in many loanwords, particularly those from Old French. For a table showing the development of the Middle English diphthongs, see Middle English phonology (diphthong equivalents).