Abstract: The diachronic development process of zhishi includes four major periods. First, the period of using zhi and shi separately where shi began to be used as a judgment verb. Second, the combination and solidification period of zhi+shi, or the transitional period where the judgment verb shi can be stably modified by the adverb zhi with the semantic focus on shi. Third, the period where zhishi is used as an adverb where the judgment function of shi weakened or disappeared with the semantic focus on zhi; meanwhile the process of semantic abscission of shi constitutes grammaticalization and the grammaticalization of shi also creates necessary conditions for the reanalysis of zhishi. Fourth, the period of zhishi being used as a turning conjunction. Since zhishi was first used as an adverb in the Tang Dynasty (618-907), its usage gradually matured. Later, the meaning of zhishi further weakened while its conjunction use gradually increased until the boundary between zhi and shi eventually disappeared.

Key words: zhi (只), shi (是), zhishi (只是), grammaticalization