本文回顧原始越語支（Vietic）的雙音節單詞到越南語單音節單詞的弱化現象（reduction）以及越南語濁輔音的發展。Thompson（1976:1131-1133）重建的越芒語支（Viet-Muong）以及後來Ferlus（1982 & 1992）重建的原始越語支都假設塞音*p/t/c/k和*b/d/ɟ/ɡ的擦音化發生在雙音節之間的位置和前音節丟失時，也因此產生越南語聲母'v' [v]、'd' [z]（來自假設的中古越南語*ð）、'gi'[z]（來自假設的中古越南語*ʒ），以及單音節詞中的'g/gh' [ɣ]。本文比較相關的原始越語支和上古漢語詞彙的重建，語音資料支持Thompson和Ferlus的假設，但同時也揭示了更複雜的情況。

This study reviews the reduction of disyllabic Proto-Vietic words to monosyllabic Vietnamese words and the development of Vietnamese voiced fricative onsets. Thompson (1976:1131-1133) in reconstructing Proto-Viet-Muong, and later Ferlus (1982 & 1992) based on his Proto-Vietic reconstructions, hypothesized the spirantization of stops *p/t/c/k and *b/d/ɟ/ɡ in previous intervocalic positions and the loss of presyllables, resulting in Vietnamese onsets 'v' [v], 'd' [z] (from hypothesized Middle Vietnamese *ð), 'gi' [z] (from hypothesized Middle Vietnamese *ʒ), and 'g/gh' [ɣ] in monosyllabic words. For this study, relevant Proto-Vietic and Old Chinese lexical reconstructions were compared, and the phonological data partially supports this claim while revealing a more complex picture. First, the changes involve classes of sounds rather than specific consonants (e.g., Vietic labial material (excluding nasals or implosives) in intervocalic position becomes Vietnamese 'v' [v] in onset position). Also, while this tendency is dominant in available data, some exceptions exist: (a) reconstructed disyllabic words for which modern Vietnamese items lack lenited onsets and (b) reconstructed monosyllabic words for which Vietnamese items have voiced fricative onsets, but without apparent conditioning factors. Evidence shows these features in modern Vietnamese developed many centuries later than in Sinitic.