定语从句是由关系代词和关系副词引导的从句,其作用是作定语修饰主句的某个成分,定语从句分为限定性和非限定性从句两种.状语从句分为时间状语从句,结果状语从句,让步状语从句,原因状语从句,条件状语从句以及行为方式状语从句.名词从句包括主语从句,宾语从句,表语从句和同位语从句及there be句型.
一、 限定性定语从句
1. that即可代表事物也可代表人,which代表事物；它们在从句中作主语或宾语,that在从句中作宾语时常可省略关系词,which在从句中作宾语则不能省略.而且,如果which在从句中作“不及物动词＋介词”的介词的宾语,注意介词不要丢掉,而且介词总是放在关系代词which的前边,但有的则放在它原来的位置
2. which作宾语时,根据先行词与定语从句之间的语义关系,先行词与which之间的介词不能丢
3. 代表物时多用which,但在带有下列词的句子中用that而不用which,这些词包括all, anything, much等,这时的that常被省略
4. who和whom引导的从句用来修饰人,分别作从句中的主语和宾语,whom作宾语时,要注意它可以作动词的宾语也可以作介词的宾语
5. where是关系副词,用来表示地点的定语从句
6. when引导定语从句表示时间
〔注〕值得一提的是,表示时间“time"一词的定语从句只用when引导,有时不用任何关系代词,当然也不用that引导
By the time you arrive in London, we will have stayed there for two weeks.
I still remember the first time I met her.
Each time he goes to besiness trip, he brings a lot of living necessities, such as towers, soap, toothbrush etc.
7. whose是关系代词,修饰名词作定语,相当于所修饰成分的前置所有格
8. 当从句的逻辑主语是some, any, no, somebody, anybody, nobody, something, anything, everything或nothing时,常用there is来引导
二、非限定性定语从句：非限定性定语从句的作用是对所修饰的成分作进一步说明,通常和主句间用逗号隔开,将从句拿掉后其他部分仍可成立
1. which引导的非限定性定语从句来说明前面整个句子的情况或主句的某一部分
2. 在引导限定性定语从句时,that有时相当于in which, at which, for which或at which
Attitudes towards daydreaming are changing in much the same way that(in which) attitudes towards night dreaming have changed. 人们对白日做梦的态度正在改变,这与人们对夜间做梦的看法的变化有非常相似之处.
I like the music for the very reason that(for which) he dislike it. 我出于某种原因喜欢这种音乐,而他恰恰与我相反.
We arrived the day that(on which) they left. 刚好我们到的那天他们走了.
3. 有时as也可用作关系代词
4. 在非限定性定语从句中,不能用that,而用who, whom代表人,用which代表事物
状语从句
§ 1状语从句的种类
用来修饰谓语动词、其它动词、定语、状语或整个句子的从句叫做状语从句.状语从句可分为：
1.时间状语从句；(adverbial clause of time)
2.地点状语从句；(adverbial clause of place)
3.原因状语从句；(adverbial clause of cause)
4.条件状语从句；(adverbial clause of condition)
5.目的状语从句；(adverbial clause of purpose)
6.让步状语从句；(adverbial clause of concession)
7.比较状语从句；(adverbial clause of comparison)
8.程度状语从句；(adverbial clause of degree)
9.方式状语从句；(adverbial clause of manner)
10.结果状语从句.(adverbial clause of result)
§2状语从句的时态特点
一般情况下,时间和条件状语从句的谓语动词一般用“一般现在时”表示“一般将来时”,用“现在完成时”表示“将来完成时”.例如：
I will call you as soon as I arrive in Beijing. 我一到北京就给你打电话.（这是由as soon as引导的时间状语从句,从句中的谓语动词arrive是一般现在时,表示一般将来时,决不可用will arrive）
As soon as I have finished this work, I will go home. 我一完成此工作,就回家.（从句中的谓语动词用现在完成时have finished,表示将来完成时,决不可用will have finished）
If he comes back, please let me know.如果他回来了,请通知我.（从句中的谓语动词用comes back,表示一般将来时,决不可用will come back）
二 时间状语从句
§3时间状语从句（adverbial clause of time）
1.由when, while, as引导的时间状语从句.例如：
When you think you know nothing, then you begin to know something.当你以为自己一无所知的时候,你就是在开始知道一些事物了.
When truth is buried under the ground it grows, it chokes, it gathers such an explosive force that on the day it bursts out , it blows up everything with it.当真理被埋在地下的时候,它在生长,它感到压抑,它蓄存着这么一种爆炸性力量,一旦冒出,它就会炸破一切!
Strike while the iron is hot. 趁热打铁.
Will you watch my clothes while I have a swim. 我游泳的时候,请你照看一下我的衣服.
You can feel the air moving as your hand pushes through it. 当你的手在空气中挥动的时候,你就能感觉到空气在流动.
Our headmaster laughed as she spoke.我们的校长边谈边笑.
【区别】when, while和as的区别：when引导的从句的谓语动词可以是延续性的动词,又可以是瞬时动词.并且when有时表示“就在那时”.例如：
When she came in, I stopped eating.她进来时,我在吃饭.(瞬时动词)
When I lived in the countryside, I used to carry some water for him.当的住在农村时,我常常为他担水.（延续性的动词）
We were about to leave when he came in.我们就要离开,就在那时他进来了.
While引导的从句的谓语动作必须是延续性的,并强调主句和从句的动作同时发生（或者相对应）.并且while有时还可以表示对比.例如：
While my wife was reading the newspaper, I was watching TV. (was reading是延续性的动词,was reading和was watching同时发生)
I like playing football while you like playing basketball.我喜欢踢足球,而你喜欢打篮球.（对比）
As表示“一边……一边”,as引导的动作是延续性的动作,一般用于主句和从句动作同时发生；as也可以强调“一先一后.例如：
We always sing as we walk.我们总是边走边唱.（as表示“一边……一边”）
As we was going out, it began to snow.当我们出门时,开始下雪了.（as强调句中两个动作紧接着先后发生,而不强调开始下雪的特定时间）
2.由before和after引导的时间状语从句.注意before引导的从句不再用否定式的谓语,并且当before引导的从句位于主句之后,有时译成“就,才”.还要注意主句和从句之间的时间关系.当主句用将来时,从句总是用现在时；如果before引导的从句谓语用的是过去时,则主句动词多用过去完成时,这样以便体现动作发生的先后.After表示主句动作发生在从句动作之后.主句和从句的动作的时间关系正好与before引导的从句相反.例如：
It will be four days before they come back. 他们要过四天才能回来.
Einstein almost knocked me down before he saw me.爱因斯坦几乎把我撞倒才看到我.
My father had left for Canada just before the letter arrived.我父亲恰好在信到之前去加拿大了.
They had not been married four months before they were divorced. 他们结婚还不到四个月就离婚了.
After you think it over, please let me know what you decide.你仔细考虑过以后,告诉我你是怎样决定的.
After we had finished the work, we went home.完成工作之后,我们回家了.（从句用过去完成时,主句用一般过去时）
3.由till或until引导的时间状语从句.till和until一般情况下两者可以互换,但是在强调句型中多用until.并且要注意的是：如果主句中的谓语动词是瞬时动词时,必须用否定形式；如果主句中的谓语动词是延续性动词时,用肯定或否定形式都可以,但表达的意思不同.例如：
I didn't go to bed until（till） my father came back.直到我父亲回来我才上床睡觉.
It was not until the meeting was over that he began to teach me English.直到散会之后他才开始教我英语.
I worked until he came back.我工作到他回来为止.
I didn't work until he came back.他回来我这才开始工作.
Please wait until I arrived.在我到达之前请等我.
4.由since引导的时间状语从句. since引导的从句的谓语动词可以是延续性的动词,又可以是瞬时动词.一般情况下,从句谓语动词用一般过去时,而主句的谓语动词用现在完成时.但在It is ＋时间＋since从句的句型中,主句多用一般现在时.例如：
I have been in Beijing since you left. 自从你离开以来,我一直在北京了.
Where have you been since I last saw you? 自上次我和你见面以后,你到哪里去了?
It is four years since my sister lived in Beijing. 我妹妹不在北京住有四年了.
It is five months since our boss was in Beijing.我们老板离开北京有五个月了.
5.由as soon as, immediately, directly, instantly, the moment, the instant, the minute, 等引导的时间状语从句.这些连词都表示“一……就”.例如：
I will go there directly I have finished my breakfast. 吃完早饭,我立即到那里去.
The moment I heard the news, I hastened to the spot.我一听到消息,马上赶到了出事地点.
As soon as I reach Canada, I will ring you up. 我一到加拿大,就给你来电话.
【注意】hardly(scarcely, rarely)…when / before, no sooner…than相当于as soon as之意.主句用过去完成时,从句用一般过去时.当hardly, scarcely, rarely和no sooner位于句首时,主句应用倒装语序.例如：
He had no sooner arrived home than he was asked to start on another journey. 他刚到家,就被邀请开始另一旅程.
No sooner had the sun shown itself above the horizon than he got out of bed to commence work.太阳刚从地平线上升起,他就起床劳动去了.
Hardly had I sat down when he stepped in.我刚坐下,他就进来了.
He had hardly fallen asleep when he felt a soft touch on his shoulder.这个阿拉伯人刚要入睡就感到肩膀上被轻轻一触.
6.由by the time引导的时间状语从句.注意时态的变化：在一般情况下,如果从句的谓语动词用一般过去时,主句的谓语动词用过去完成时；如果主句的谓语动词用一般现在时,主句的谓语动词用将来完成时.例如：
By the time you came back, I had finished this book.到你回来时,我已经写完这本书了.
By the time you come here tomorrow, I will have finished this work. 你明天来这儿的时候,我将已经完成此工作了.
7.由each time, every time和whenever引导的时间状语从句.例如：
Each time he came to Harbin, he would call on me. 他每次来哈尔滨,总是来看我.
Whenever that man says“To tell the truth”, I suspect that he's about to tell a lie.每当那个人说“说实在话”的时候,我猜想他就要说谎了.
You grow younger every time I see you. 每次遇到你,见你更年轻了.
8.由as long as和so long as引导的时间状语从句.这两个连词表示“有多久……就多久”.例如：
You can go where you like as long as you get back before dark. 你可以随意到哪里去,只要在天黑以前回来就行.
I will fight against these conditions as long as there is a breath in my body! 只要我一息尚存,我就要反对这种境况.
三 地点状语从句
§4地点状语从句 (adverbial clause of place)
地点状语从句一般由连接副词where, wherever等引导,已经形成了固定的句型,例如：
句型1：Where＋地点从句,（there）＋主句.
【注意】此句型通常译成“哪里……哪里就……”；主句在从句后面时,there可用可不用；如果主句在从句的前面时,一般都不用there.例如：
Where there is no rain, farming is difficult or impossible.在没有雨水的地方,耕作是困难的,或根本不可能的.
They were good persons. Where they went, there they were warmly welcomed. 他们都是好人.因此他们走到哪里都受到热烈欢迎.
You should have put the book where you found it. 你本来应该把书放回原来的地方.
Where the Communist Party of China goes, there the people are liberated.哪里有了中国共产党,哪里人民得解放.
句型2：Anywhere/ wherever＋地点从句,＋主句.
【注意】anywhere本身是个副词,但是,常可以引导从句,相当于连词,意思相似于wherever, anywhere引导的从句可位于主句之前,也可以位于主句之后. 而wherever本身就是个连词,表示“在何处,无论何处”.例如：
Wherever the sea is , you will find seamen.有海就有海员
同位语
一个名词(或其它形式)对另一个名词或代词进行修饰,限定或说明,这个名词(或其它形式)就是同位语.同位语与被它限定的词的格要一致,并常常紧挨在一起.
1.由两个或两个以上同一层次的语言单位组成的结构,其中前项与后项所指相同,句法功能也相同,后项是前项的同位语.
Mr. Smith, our new teacher, is very kind to us.
我们的新老师史密斯先生对我们很好.
Mr. Smith是主词our new teacher的同位语,指同一人.
Yesterday I met Tom, a friend of my brother's.
昨天我遇到了我弟弟的朋友汤姆.
a friend of my brother's是受词Tom的同位语,指同一人.
2.如同位语与其同位成分关系紧密时不用逗点隔开;如同位语对其同位成分只作补充解释时可用逗点隔开.
He himself told me that his brother John is a world-famous doctor.
他本人对我讲,他的兄长约翰是一位世界闻名的医生.
himself和John都是单一的字作同位语,与其同位成分之间不用逗点隔开.
Yesterday I talked to my English teacher, Mr. James.
昨天我与我的英语老师詹姆斯先生谈过了.
同位语Mr. James补充解释my English teacher,同位语与其同位成分之间可用逗点隔开.
3.同位语除表示其同位成分的全部意义外,还可以表示部分意义.
We Chinese people are brave and hardworking.
我们中国人民是勤劳勇敢的.
He is interested in sports, especially ball games.
他喜欢运动,特别是球类运动.
同位从句一般跟在某些名词如answer(答案),hope(希望),fact(事实),belief (信仰),news(消息),idea(主意；观念),promise(承诺),information(信息),conclusion(结论),order(命令), suggestion(建议),problem(问题),thought (想法)等后面.例如： He always works hard even if he knows the fact that he is not in good health. His failure was due to the fact that he had not practised for a long time. I had no idea that you were here. She told us her hope that she would become a pianist. He made a promise that he would never come late. 注意： that 既可引导同位语从句又可引导定语从句,其区别在于：同位语从句由连接词that引导,连接词that本身无意义,在同位语从句中不充当任何成分,不可省略,不可以用其他词替代；定语从句由关系代词that引导,关系代词that在从句中充当一定的成分,作宾语时可省略,由when, why, where引导的 同位语从句和定语从句的区别在于： 同位语从句由连接副词只起连接作用,没有指代作用； 定语从句由关系副词引导,关系副词具有指代先行词的作用,常用一个介词加关系代词替换.例如:I will never forget the day when we first met. （同位语从句, when为连接词） That is the special day (which/that) I will never forget. （定语从句,which/that为关系副词） This is the house where we lived fifteen years ago. （同位语从句, where为连接词） This is the house which we sold fifteen years ago. （定语从句,where为关系副词）
区分表语从句和同位语从句
从句是相对于主句而言的,即它是从属于某一个主句,而不能单独作一个句子.在英语中,主要有三大从句,即名词性从句（包括主语从句,宾语从句,表语从句,同位语从句）、形容词性从句（即定语从句）、副词性从句（即状语从句,包括时间、条件、结果、目的、原因、让步、地点、方式等）.
主语从句用作主语,如：：
That the earth is round is true. 地球为圆的是真实的.
宾语从句用作宾语.如：
Do you know where he lives?
表语从句用作表语,如：
My opinion is that you should not go alone. 我的意见是你不应单独前往.
同位语从句用于解释说明前面的名词.如：
The fact that the earth is round is true. 地球是圆的的事实是真实的.（that从句用于解释说明the fact）
定语从句相当于一个形容词,用于修饰前面的名词.如：
The student who answered the question was John. 回答问题的学生是John.
状语从句相当于一个副词,如：
When it rains, I usually go to school by bus. 天下雨时,我通常坐公共汽车上学.（时间状语）
If he comes tomorrow, you will see him. 如果他明天来,你就可以看见他.（if 引导的条件状语从句,其结构为：if +状语从句,＋主句）.要注意在状语从句中有一个规则是“主将从现”,即主句是将来时,则从句要用一般现在时表示将来.
主句和从句的划分方法是相同的.句子的成分从谓语动词处来划分比较容易.谓语动词前面的部分是主语,后面常接宾语,修饰谓语动词的是状语,修饰主语、宾语的是定语,若谓语是系动词,则系动词后的部分是表语.如：
I am a teacher. 其中,I 是主语,am是谓语,a teacher 是表语.
He likes playing football very mucy. 其中,he是主语,likes是谓语,playing football是宾语,very much是状语.
参考资料：http://zhidao.baidu.com/question/45927224.html?fr=qrl