The Arc. Ch. vowel system, as reconstructed by Karlgren, comprises some 10 vowel phonemes, half of which are distinguished quantitatively:

Front vowels: i; ĕ∼e; ε

Back vowels: ŭ∼u;

Central vowel: ǝ

Low vowels: â; ӑ∼a

It is apparent that this vowel system is far richer than anything to be found in Tibeto-Burman, and indeed serious difficulties arise in comparative analysis. In final position only the following vowels (all long) are found: a, â, å, o, and u. Final i appears only as the first member of a diphthong, while e, ε, ô, and ǝ appear only before final stop, nasal, or -r. The dissimilarity of the two systems, then, extends even into the features of distribution.

Diphthongization, as already pointed out by the writer (Benedict, 1940), is the keynote of the development of vowels in Ar. Ch. This feature is best revealed in the Ar. Ch. treatment of original medial *i before surd stops and nasals (*i>-įĕ-):

sįĕn ‘firewood’; TB *siŋ ‘tree, wood’ (Trung also ‘firewood’).

sįĕn ‘bitter’; TB *m-sin ‘livery’ <*sin ‘bitter, sour’.

mįĕn ‘order, command’ (this earlier reading for mįӑng is revealed in several Shih Ching rimes); cf. B mín, id.

įĕt ‘1’; cf. Kanauri id.

ńįĕt ‘sun, day’ (with suffixed -t); TB *niy.