but,whileyesterday. （而，尽管） 约翰喜欢打篮球，但他昨天没打。 nevertheless(然而；不过) We must hurry, or we’ll miss the train. 选择关系or, 我们必须快点，否则会赶不上火车。 otherwise or else, Either you come to my place or I go to yours. either…or 或者你到我这儿来，或者我到你那去。 We had better stay at home, for it was raining. 因果关系for, 我们最好呆在家里，因为天正在下雨。 so, thus, therefore, He didn’t work hard, therefore he failed in the examination. and so 他学习不努力，因此这次考试不及格。 由一个主句和一个或一个以上的从句构成的句子叫复合复句。在复合句合中主句是全句句 的主体，从句是全句的一个成分，不能独立。 II.状语从句
状语从句是每年高考必考的内容，在高考试题中加上其它从句的干扰，以及倒装句，强调句的介入，使得状语从句更为复杂。 1.时间状语从句
由下列连词引导：when,while,as,before,after,once,till,until,since,as soon as,now that,hardly…when,
从句有： 名词性从句（主语从句，表语从句，宾语从句和同位语从句） 状语从句 定语从句 （详细请看以下内容）
scarcely…when,no sooner…than,有一些表示时间的副词(短语)或名词短语也可引导时间状语从句。如：directly,instantly,immediately,by the time，the moment,the second,the minute,the instant,every time,each time,next time,the last time等 重点内容如下：
①when,while,as引导的时间状语从句
▲as表示“当……的时候”，往往和when/ while通用，但它着重强调主句与从句的动作或事情同时或几乎同时发生。 She came up as I was cooking.(同时)
The runners started as the gun went off.(几乎同时)
▲when(at or during the time that )既可以表示在某一点的时候，又可表示在某一段时间内，主句与从句的动作或事情可以同时发生也可以先后发生。 It was raining when we arrived.(指时间点)
When we were at school, we went to the library every day.(在一段时间内)
When we arrived there,the film had already begun.(先后发生) ▲while意思是“当……的时候”或“在某一段时间里”。主句中的动作或事情在从句中的动作或事情的进展过程中发生，从句中的动词一般要用延续性动词。在when表示a period of time时，两者可以互换。
Please don’t talk so loud while/when others are working. He fell asleep while/when reading.
Strike while the iron is hot.( 不可用as或when，这里的while意思是“趁……”)
②before状语从句的重点句型
▲……之后……才：It was a long time before I got to sleep . ▲不多久……就：It wasn’t long before he told me about the affair. ▲不等……就：Before I could get in a word, he had measured me. ▲刚……就：He hardly entered the room before he heard the telephone ring.
▲先……再：You can have a few days to think about it before you make your decision.
③since 引导的从句用延续性动词的过去式(包括过去完成时)，则从句的动作已经结束,从句意思是否定的。如果从句的动词是延续性的用完成时态，从句意思是肯定的。
▲He has never been to see me since I was ill.我病愈后，他一直未来看我。(不在生病了)
▲He has never been to see me since I have been ill.我病了，他一直未来看我。
▲I haven’t heard from him since he lived here. 自从他这里搬走，我就没有收到他的信。(不住在这儿了)
▲I know him very well since he has lived here near us.自他住在我们附近以来，我对他很了解。
▲It’s three years since I was in the army.我退伍已三年了。(不在服役了) ▲It’s three years since I have been in the army=It's three years since he joined the army. 我入伍已三年了。
④如果与till与until从句使用的主句是肯定的，则主句中谓语要用延续性动词如果与其使用的主句是否肯定的，则主句中谓语要用短暂性动词。另till从句不可以置于句首，只有until从句可以放在句首。not until 放在句首时主句要倒装。
2.原因状语从句
由下列连词引导：as(由于),because(因为), since(既然),now (that) (既然), considering that(顾及到), seeing that(由于)。
I do it because I like it.因为我喜欢我才干。(because不能与 so连用) He couldn’t have seen me, because I was not there.他不可能见过我，因为当时我不在那儿。
Seeing (that) quite a few people were absent, we decided to put the meeting off.
由于好些人都没到会，我们决定延期开会
Now that/Since you are all here, let’s try and reach a decision. 既然大家都来了咱们就设法做一个决定吧
As she was ill, she didn’t come to the party. 由于病了，她没来参加晚会。
Considering that they are just beginners, they are doing quite a good job.
考虑到他们才刚刚学做，他们干得算很不错的了。 重点内容如下：
①because语气最强，用于回答why的提问，可与强调词only,just 以及否定词not 连用。但不可以与so连用。如You shouldn’t get angry just because some people speak ill of you.另外注意与not连用时否定的转移。He didn’t do such a thing because he was afraid of his wife.他并不是因为怕他的妻子才做这样的事。
Cf:He didn’t do such a thing,because he was afraid of his wife.因为怕妻子，他没有做这样的事。 because引导的从句可以被强调：
It was because she wanted to study abroad that she entered for TOEFL
②as语气较弱，since语气也较弱，但比as正式一些,所说明的原因比较明显或是已知的事实，多用于口语中，所以不应该强调。常置于句首。 As all the seats were full,he stood there. Since you are going,I’ll go,too.
③for虽解释为“因为”但只是一个并列连词，它引导的是并列句，不是原因状语从句。
The day was short,for it was December. 3.地点状语从句
由下列连词引导:where,wherever,anywhere,everywhere。 Anywhere he went,he got warm welcome.