Vowels in the unstressed position
All vowels in the unstressed position changed and became [ə] or [i] unstressed. This phonetic change had a far-reaching effect upon the system of the grammatical endings of the English words, which now due to the process of reduction became homonymous. For example:
- forms of strong verbs
OE writan- wrāt – writon– writenwith the suffixes –an, -on, -endifferent only in the vowel component became homonymous in ME:
written– wrōt – writen– writen
- forms of nouns
OE nominative plural a-stem fiscas
genitive singular fisces
OE dative singular fisce
genitive plural fisca
Vowels under stress
In the ME period a great change affected the entire system of vowel phonemes.
OE had both short and long vowel phonemes, and each of these could occur in any phonetic environment, i.e. they were absolutely independent phonemic units.
As a result of important changes coming into the vowel system in the 10th – 12th centuries, the ME vowel system was basically different. While in OE quantity (i.e. length/shortness) was a distinctive phonemic feature, in ME (by the 13th century) quantity of vowels becomes dependent on their environment – to be exact, on what follows. In some phonetic environments only short vowels can appear, while in other phonetic environments only long vowels can appear.
Changes of monophthongs
Three long monophthongs underwent changes in Middle English:
The rest of the monophthongs retained their original quality, for example:
ē < ee tēþēþ teeth
ō < oo tōþōþ tooth
ū < ou ūt out
ī < ii tīma time
Out of seven principal OE short monophthongs: a, e, o, i, u, æ, y – two changed their quality in ME:
[æ] > [a] pæt that
[y] > [i] fyrst first
but the rest of the monophthongs remained unchanged, e. g:
Changes of diphthongs
One of the most important sound changes of the Early ME period was the loss of
the OE diphthongs and the growth of new diphthongs. OE possessed a well developed
system of diphthongs. Towards the end of the OE period all the diphthongs were contracted (i.e. became monophthongs).
Development of Old English diphthongs in Early Middle English
As a result of these changes the vowel system lost two sets of diphthongs, long and short. In the meantime a new set of diphthongs developed from some sequences of vowels and consonants due to the vocalization of OE [j] and [γ], (i.e. to their change into vowels).