The present study attempts to trace historically diachronic changes in the usage of the subordinator yadā in Sanskrit, focusing on the syntactic aspect of yadā-clauses. The result is that the presence or absence of a correlative structure is mainly influenced by two factors: the period of the text in question （i.e., Vedic, Epic, and Classical） and the distinction between verse and prose. Specifically, the ratio of the correlative structure decreases as time goes by, being significantly higher in prose than in verse. As for the correlating demonstrative adverbs, there is a gradual diachronic change from Rigvedic ā́d to Post-Rigvedic Vedic áthā̆, then finally to Epic and Classical tadā.
