条件状语从句 我们知道, 引导条件状语从句最常用的连词是if, 由if引导的条件状语从句表示在某种条件下某事很可能发生。如: If you ask him, he will help you. 如果你请他帮忙, 他会帮你的。 If you fail in the exam, you will let him down. 另外, if从句还表示不可实现的条件或根本不可能存在的条件, 也就是一种虚拟的条件或假设, 从句多用一般过去时或过去完成时。如: If I were you, I would invite him to the party. I would have arrived much earlier if I had not been caught in the traffic. 如果没有堵车, 我会到的早一点儿。 其他的连词: 1.unless conj. 除非, 若不, 除非在…的时候 You will fail to arrive there in time unless you start earlier. 如果你不早点动身, 你就不能及时赶到那儿。 Unless it rains, the game will be played. 除非下雨, 比赛将照常进行。 2. on condition (that)...在……条件下, 如果; on condition (that)...引导的条件从句是主句事件发生的前提条件或唯一条件。 I can tell you the truth on condition that you promise to keep a secret. 我可以告诉你真相, 条件是你答应保守秘密。 You can go swimming on condition (that) you don’t go too far from the river bank. 你只有在不远离河岸的条件下才可以下水游泳。 3. supposing conj. 如果, 假如 supposing引导的条件从句表示一种假设条件 Supposing it rains, shall we continue the sports meeting? 倘若下雨, 我们的运动会还要继续举行吗? Supposing something should go wrong, what would you do then? 假如出了什么问题, 你准备怎么对付? Supposing it rains, shall we continue the sports meeting? 倘若下雨, 我们的运动会还要继续举行吗? Supposing something should go wrong, what would you do then? 假如出了什么问题, 你准备怎么对付? 4. provided conj.假如,除非,以……为条件 provided (that) +从句表示一种假设条件。 He will sign the contract provided we offer more favorable terms. 如果我们提出更优惠的条件, 他就会在合同上签字。 He won’t be against us in the meeting provided that we ask for his advice in advance. 如果我们提前征求一下他的意见, 他就不会在会上反对我们。 另外还有in case, as/so long as In case it rains, do not expect me. 如若下雨, 就不要等我了。 As long as you promise to come, I’ll wait for you until you come. 只要你答应, 我就等你来。 从上述例句可以看出if, unless, on condition (that), supposing, provided等词引导的条件状语从句,主从句条件关系分明, 结构清晰。 在条件状语从句中, 用一般现在时代替一般将来时, 一般过去时代替过去将来时。 本文来源：https://www.wddqw.com/doc/4e6d6609084c2e3f5727a5e9856a561252d321e3.html