本文研究臺灣南島語言補語句動詞主焦標記限制以及其形成的機制。研究發現，遵守該限制之補語句為一非限定、不完整之輕動詞詞組。主焦標記限制不僅出現在結構重整句，也出現在非結構重整句。不過，不管哪一種句型，主句動詞都高度受限：前者主句動詞限於結構重整動詞，後者限於具有域外論元的動詞。在結構重整句裡，主句動詞之域外論元為一惰性論元，不阻隔補語句之賓語提升，形成主句非主焦、補語句主焦的格局；在非結構重整句裡，主句動詞之域外論元為一活性論元，會阻隔補語句的賓語提升，因此補語句不能為非主焦。總之，主焦標記限制為多個因素作用之結果，其中最重要的為局部性條件。

Under a generative framework, this paper investigates the properties of the AV-only restriction on complementation and how it comes about across many Formosan languages. It is found that the AV-only complements occur as a nonfinite defective vP without any formal feature and that they are tenselss and subjectless—temporal markers must attach to the matrix verb; the embedded object, if any, is required to move to the matrix subject position to get case. The AV-only restriction is attested not only in restructuring constructions but also in non-restructuring ones. In both types, the matrix verbs are highly restricted: in the first type, the matrix verb is restricted to a restructuring verb and in the second type, the matrix verb is limited to a verb that projects an external argument. In restructuring contexts, the matrix external argument, if there is one, is inert and creates no intervention effects for the shifted embedded object; in non-restructuring contexts, the matrix external argument blocks the raising of the embedded object, thereby preventing the embedded verb from occurring in the non-AV transitive form. The AV-only restriction is due to multiple factors, most important of which is a locality condition.