在诸多条件状语从句中,由only if和if only引导的条件从句虽然都可用来表示主句所需要的“条件”概念,但二者在表示说话人的语义意图却有值得注意的差异。本文拟说明如下。1.only if…Only放在由if引导的条件状语从句之前,构成的则是一个对“条件”限制更严的“限制性条件从句”,用来表示只有当……(才);只有在……的时候 In many conditional adverbial clauses, although the conditional clauses guided by only if and if only can be used to represent the concept of the “conditionality” required for the main sentence, there are significant differences between the two in expressing the semantic intention of the speaker. This article is intended to explain as follows. 1.only if...Only placed before the conditional adverbial clause guided by if constitutes a more restrictive “conditional clause” that restricts the “condition”, used to indicate that only if ... (only); only ……when