3．原因状语从句
　　1）because表示人们不知道的直接的原因或理由，着重点在从句，即because引出的从句为全句句意的中心所在。通常用于回答why提出的疑问，语气最强，除了特别强调外，该从句一般位于主句后面。
　　since表示对方已知的、无须加以说明的既成事实的理由。全句的中心在主句上，语气比because弱，译为“既然”。引出的状语从句一般放在句首。
　　as表示十分明显的原因，一般说明因果关系，着重点在主句，语气更弱，常译为“由于”。引出的状语从句一般放在句首。
　　for 引出的分句，语气最弱，主要是补充说明原因，解释另外一个分句，且只能放在句子后部。
　　如：I didn’t go abroad with her because I couldn’t afford it.我没有和她一起出国是因为费用太高。
　　Since traveling by air is much faster, they decided to take a plane.既然乘飞机旅行快得多，他们就决定坐飞机。
　　As it is snowing, we shall not climb the mountain.由于在下雪，我们就不爬山了。
　　It must have rained last night, for the ground is wet.昨晚准下雨了，地面是湿的。
　　2）now that, seeing that, considering that, in that表示鉴于，由于。in that只能放在主句之后。
　　如：Now that you have passed your test, you can drive on your own.你驾驶考试既然已经合格，就可以独自开车了。
　　Seeing that the weather is bad, we’ll stay at home.由于天气不好，我们要呆在家了。
　　I am in a slightly awkward position, in that he’s not arriving until 10th.我的处境有点难堪，因为他要十号才来。
　　4．条件状语从句
　　1）if (如果),unless（除非）; unless相当于if not.
　　如：I will buy a computer if I am able to save up enough money. 如果我能存下足够的钱，我就买台电脑。
　　Unless the weather was bad, my father always used to take a walk in the evening.除非天气不好，我的父亲晚上总是去散步。
　　2）suppose/supposing that, provided/providing that(假如)
　　如：Supposing that it rains, can we play the match indoors?要是下雨，我们在室内比赛行吗？
　　Ｉwill agree to go provided that my expenses are paid.假如为我负担费用，我就同意去。
　　5．让步状语从句
　　although, though引导让步状语从句，主句不能用 “but”.
　　如：Although they lack official support, they continue their struggle.他们虽然没有得到官方的支持，但仍然继续奋斗。
　　as虽然，尽管。引导让步状语，常放在作表语、状语的形容词、名词、副词后面。
　　如：Strong as you may be, you can not lift it. 尽管你可能很有力气，你却无法把他提起来。
　　Hard as he tried, he was unable to make much progress.他虽然竭尽全力，但是没有取得多大的进步。
　　6．目的状语从句
　　so that, in order that . 引导目的状语从句,从句的谓语常用can, could, may, might, shall, should, will, would等情态动词。in order that可以位于主句的前面或后面。so that引导的从句只能放在主句之后。
　　如：They started early so that they might arrive in time.他们早点动身，以便准时到达。
　　In order that they could go around West Lake, they stopped at Hangzhou.为了游览西湖，他们在杭州停了下来。
　　7．结果状语从句
　　1)so …that; such…that表示“如此……以至于”
　　so 后面通常接形容词或副词。such后面通常为名词。如果名词前有many, much, 等修饰，要用so…that.
　　such+a/an+adj+单数名词+that可以换成so+adj.+a/an+单数名词+that
　　如：There is so little time left that I have to tell you about it later.现在剩下的时间不多了，我只只好以后再给你讲这事。
　　He told us such a funny story that we all laughed.
　　He told us so funny a story that we all laughed.
　　2003年第17小题：
　　It was ____that a hundred people looked lost in it .
　　A so a large room B a so large room C such a large room D such large a room
　　2) so that“以至于，所以”。引导的结果状语从句之前可以有逗号。
　　如：She phoned me on arrival so that I knew she was safe and sound.她到达之后给我打了电话，我知道她平安无恙。
　　注：so that可以引导结果状语从句也可以引导目的状语从句，除了根据句意来判断外，还可以根据结构形式来判断。若从句前有逗号，一般为结果状语从句。如果从句中有情态动词，一般则为目的状语从句。
　　如：They started out early, so that they did not miss the train.他们早早出发了，所以没有误了火车。（结果状语）
　　They started out early so that they would not miss the train.他们早早出发是为了不误火车。（目的状语）
　　8．方式状语从句
　　1）as(正如)引导方式状语从句
　　如：She enjoys all kinds of music, as I do.她各种音乐都喜爱，和我一样。
　　Why didn’t you catch the last bus as I told you to?你怎么不听我的话赶乘末班公共汽车呢？
　　注：口语中like可以用作连词，当作as 使用。
　　如：Nobody understands him like /as I do. 没有人能像我这样理解他。
　　2)as if/though（好像）引导方式状语从句往往用虚拟，表示与事实相反。
　　如：They looked at me as if /as though I were mad.他们看着我好像我发疯了似的。
　　9．比较状语从句(在比较级结构中讲过)