本文認為時間副詞「在」的功能可以表動作進行或狀態持續。這兩種來源不同，表狀態持續義是「處所動詞＞時間副詞」的演變，這是在靜態語境中，誘發隱喻機制而形成。表動作進行義則是「處所動詞＞處所介詞＞時間副詞」的演變，這是在動態語境中，連動結構發生語義級降後，再藉由「在+指示代詞」的虛指用法，進而脫落處所詞而產生。此兩條演變途徑，具類型學上意義，可藉由跨語言比較得到印證。時間副詞「正在」的形成是在因果語境中，「〔正〕_(副)+〔在+VP〕_(動賓／介賓)」無法以「正+在+VP+之時」解釋，使VP轉為動作事件焦點，而重新分析為「〔正在〕_(副)+〔VP〕_(動詞組)」。

This study argues that the functions of the time adverb zai 在 can express action progression and state continuance. These two functions stem from different sources. Zai 在, functioning as state continuance, involves the evolution of {locative verb ＞ time adverb}. This was formed by inducing a metaphor mechanism in the static context. Zai 在, which performs action progression, evolved from {locative verb ＞ locative preposition ＞ time adverb}. This happened in the dynamic context where serial verb constructions carried out semantic devaluation and the void reference of {zai 在 + demonstrative pronoun} caused the dropping of the locative phrases. The two evolution routes take on typological meaning and are confirmed via cross-linguistic comparison. The time adverb ＂zhengzai＂正在 was formed in the cause-effect context where the sequence {＂zheng 正＂_(adverb) + ＂zai 在 + VP＂_(verb-object/preposition-object)} cannot be explained by {zheng 正 + zai 在 + VP + zhishi 之時}. The ＂VP＂ was then turned into the focus of action events, which led to a reanalysis as {＂zhengzai 正在＂_(adverb) + ＂VP＂_(verb phrase)}.