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Phonetics and Phonemics in Historical Linguistics-i
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// / /u/ lül /e/
10/
/a/ // eight phonemes on the whole.
This system assymetrically because the two mid vowels are indifferent to length. We have a choice to put them with the short or the long series, leaving a gap in the other. Because the long allophones have greater freedom of occurrence we may choose to put them along with i ū and á and present the system as follows:
short
long // /u/ W /ū/
lē/ //
/a/
// We now compare the phonemic systems of the OIA and MIA. We note a great change between the two and a sudden jump or a drastic modification of the vowel system: While the system of the short simple vowels remains the same, the whole system of the diphthongs disappears. The system of the long vowels gets modified by the addition of two more phonemes lē/ and /o/ and there is a corresponding gap in the series of the short vowels. One gets the impression of a good deal of sudden change in the system, which is likely to remain unexplained.
We, however, know what has happened to the vowels of the OIA when they pass on to the MIA stage. Very few phonetic changes have occurred, and all of them are the result of the same basic tendency which is perfectly understandable provided we are willing to look at them in their concrete phonetic forms. Following a drift, which has its beginnings even in pre-Indo-Aryan stage, the changes are all in the way of reducing the length of vowels by one mora under certain definite conditions, thus reducing the long diphthongs to short ones and the short diphthongs to monophthongs in the OIA stage. The same tendency has changed the short diphthongs of OIA to monophthongs in the MIA and all vowels are shortened before a consonant-cluster or in a closed syllable. We can tabulate the changes as follows: Pre-OIA OIA
MIA
o oro au
o oro
au