越南語的極性問句是將一個否定助詞加在肯定句之後而形成的。現代越南語中有三種否定助詞，但卻只有其中兩種可以置於肯定句後使之形成問句。本文為此現象提出了一個分析。此分析是基於將極性問句分析為備選集，並利用從歷史文本中發現的歷時變化事實進行推理。

Polar questions in Vietnamese consist of an affirmative sentence followed by a negation particle. Modern Vietnamese has three negation particles, but only two can occur in this function. This note proposes an account for this gap. The account is premised on the analysis of questions as sets of alternatives, and draws on facts of diachronic change gleaned from historical texts.