Development of diphthongs
The PG diphthongs – [ei, ai, iu, eu, au] – underwent regular independent changes in Early OE; they took place in all phonetic conditions irrespective of environment. The diphthongs with the i-glide were monophthongised into [i:] and [a:], respectively; the diphthongs in –u were reflected as long diphthongs [io:], [eo:] and [ea:].
The PG diphthongs (or sequences of monophthongs, see § 56) — [ei, ai, iu, eu, au] — underwent regular independent changes in Early OE; they took place in all phonetic conditions irrespective of environment. The diphthongs with the i-glide were monophthongised into and [a:], respectively; the diphthongs in -u were reflected as long diphthongs [io:], [eo:] and [ea:]. (The changes are shown in Table 2.)
Ifthe sounds in PG were not diphthongs but sequences of two separate phonemes, the changes should be defined as phonologisation of vowel sequences. This will mean that these changes increased the number of vowel phonemes in the language. Moreover, they introduced new distinctive features into the vowel system by setting up vowels with diphthongal glides; henceforth, monophthongs were opposed to diphthongs.
Table 2
Old English Reflexes of Proto-Germanic Diphthongs
(or Bi-Phonemic Sequences)
| Change illusirated | Examples | |||
| PG | OE | Other OG languages | OE | NE |
| a + i | a: | Gt stains Gt ains | stān ān | stone one |
| e + i | i: | Gt meins[11] Gt reisan | min risan | mine, my rise |
| a + u | ea: | O Icel austr Gt auso Gt augo (cf. G Auge) | ēast ēare ēaʒe | east ear eye |
| e + u | eo: | Gt piudans Gt kiusan | pēoden | ‘king’ choose |
| i + u | io; | Gt diups | dēop, diop[12] | deep |
One of the most important sound changes of the Early ME period was the loss of OE diphthongs and the growth of new diphthongs, with new qualitative and quantitative distinctions. OE possessed a well developed system of diphthongs: falling diphthopgs with a closer nucleus and more open glide arranged in two symmetrical sets long and short: [ea:, eo:, ie:] and [ea, eo, ie]. Towards the end of the OE period some of the diphthongs merged with monophthongs: all diphthongs were monophthongised. In Early ME the remaining diphthongs were also contracted to monophthongs: the long [ea:] coalesced with the reflex of OE [ æ:] ME[ ]; the short [ea] ceased to be distinguished from OE [æ] and became [a] in ME; the diphthongs [eo:, eo] -- as well as their dialectal variants [io:, io] - fell together with the monophthongs [e:, e, i:, i ]. Later they shared in the development of respective monophthongs. As a result of these changes e 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 vocalisation of OE [j] and [y], that is to their change into vowels.
In Early ME the sounds [j] and [y] between and after vowels changed into [i] and [u 1 and formed diphthongs together with the preceding vowels. These changes gave rise to two sets of diphthongs: with i-glides and u-glides.
The formation of new diphthongs in ME was an important event in the history of the language.
