在语言学中，当两个语言成分（辅音、元音、词素等）不能在同一个环境中出现，即处于互补分布。

当两个以上的语音成分处于互补分布时，这两种成分一般可以视为同一个音位的条件变体。

但是，这个原则仍然有一些特例，因为当两个语音成分之间没有任何共同的语音特征—尽管这两个语音成分处于互补分布，很难断定它们是否同一个音位的变体。例如，英语的[h]只出现在词首，[ŋ] 只出现在词尾，显示出明显的互补分布，但由于这两个辅音没有共同的语音特征，从来不发生交替，没有历史关系等原因，因此一般语言学家认为是两个独立的音位。

In linguistics, complementary distribution, as distinct from contrastive distribution and free variation, is the relationship between two different elements of the same kind, where one element is found in one set of environments and the other element is found in a non-intersecting (i.e. complementary) set of environments. It often indicates that two superficially different elements are the same linguistic unit at a deeper level. It is possible for more than two elements to be in complementary distribution with one another.