This paper deals with the evolution of the Russian indefinite series to and nibud’ after the 18th century. The Russian National Corpus data show that in the 18th–19th centuries, to was almost strictly specific, while nibud’ was slightly less non-specific compared to modern Russian. In the 20th century, to expanded to non-specific contexts but, crucially, did so inconsistently: it overtook nibud’ in frequency in conditionals and questions, but not in imperatives. These facts raise the following questions: (i) What triggered the expansion of to? (ii) Why was this expansion inconsistent? The answers that I suggest are as follows: (i) to expanded because its relationship with nibud’ was close to that of complementary distribution, which is a typologically rare, hence, unstable situation. (ii) to expanded to those non-specific contexts that helped to accommodate the originally specific semantics of to to the non-specific meaning of the context.

本文论述了18世纪以后俄语不定系列to and nibud'的演变。俄罗斯国家语料库数据显示，在 18-19 世纪，to几乎是严格特指的，而nibud'与现代俄语相比，非特指程度稍低。在 20 世纪，to扩展到非特定语境，但最重要的是，它的做法不一致：它在条件句和疑问句中的频率超过了nibud'，但在祈使句中却没有。这些事实提出了以下问题： (i) 是什么触发了to的扩展？(ii) 为什么这种扩展不一致？我建议的答案如下： (i )之所以扩大，是因为它与尼布德的关系接近于互补分布，这在类型上是罕见的，因此是不稳定的情况。(ii)扩展到那些非特定上下文，有助于将to最初的特定语义适应上下文的非特定含义。