英语语法
英语句子成分：
组成部分：包括主语、谓语、宾语、定语、状语、表语、同位语七种
1.主语是句子叙述的主体，可由名词、代词、数词、名词化的形容词、不定式、动名词和主语从句等来承担。
2.谓语说明主语所发出的动作或具有的特征和状态。谓语由动词来承担。
3.宾语是动作的对象或承受者，常位于及物动词或介词后面。宾语可由名词、代词、数词、名词化的形容词、不定式、动名词、宾语从句等来担任。
4.定语是用于描述名词，代词，短语或从句的性质，特征范围等情况的词，定语可以由名词，形容词和起名词和形容词作用的词，短语担任。如果定语是单个词，定语放在被修饰词的前面，如果是词组，定语放在被修饰词的后面。
5.状语说明事物发生的时间，地点，原因，目的，结果方式，条件或伴随情况，程度等情况的词叫状语。状语一般由副词、介词短语、分词和分词短语、不定式或相当于副词的词或短语来担当。其位置一般放在句末，但也可放在句首或句中，修饰动词、形容词、副词等
6.表语是用来说明主语的性质，身份，特征和状态。表语须和连系动词一起构成句子的复合谓语。表语一般放在系动词之后。表语可以由名词，形容词或起名词和形容词作用的词和短语担任。
7.当两个指同一事物的句子成分放在同等位置时，一个句子成分可被用来说明或解释另一个句子成分，前者就叫做后者的同位语（appositive）.这两个句子成分多由名词（代词）担任，同位语通常皆放在其说明的名词（代词）之后。
另：补语的作用对象是主语和宾语，具有鲜明的定语性描写或限制性功能，在句法上是不可或缺的。补语是起补充说明作用的成份。最常见的是宾语补足语。名词、动名词、形容词、副词、不定式、现在分词、过去分词都可以在句子中作宾补。 I find learning English difficult.(difficult是形容词做宾补） The first truck is carrying a few baskets. （主谓定表）
The doctor looked over Mrs. Brown very carefully.（主谓宾状） I find learning English difficult.(difficult是形容词做宾补）（主谓宾补）
This is Miss Chen,our English teacher.（主谓同位）
句子类型：定语从句，宾语从句，状语从句，同位语从句，主语从句 定语从句的用法
(一) 定语从句的作用
作用 在句子中作定语,修饰句子中的某一名词或代词,从句须放在先行词之后。 关联词 关联词用于引导一个定语从句,代替先行词在从句中充当一定的成分。
(二) 关系代词的作用
作用例句
1.作主语1. The student who is talking with the monitor is Lucy.（指人作主语）
2. A dictionary is a book which gives the meaning of words.（指物作主语）
2.作表语 3.She is no longer the girl that she used to be.（指人作表语）
3.作宾语 The student whom (who)you want to see has come already.（指人作宾语）
5.The letter which I received yesterday was from a friend of mine.（指物作宾语）
4.作定语 6.The girl whose mother is a teacher studies very hard.（指人作定语）
(三) 须用that引导的定语从句
1.nothing,everything,anything,much, all, little等不定代词作先行词时，常用that引导从句.something两者均可。 Is there anything that I can do for you?
2.指物的先行词前被序数词修饰时。 The first thing that we should do is to help him.
3.指物的先行词前被形容词最高级修饰时。 This is the best foreign film that I have ever seen.
4.指物的先行词前被the very, the only, the same修饰时。 That’s the very tool that we are looking for.
5.先行词既指人又指物时。They talked about the things and friends that they could remember.
6.主句是由Who/Which引导的特殊疑问句时。 Who is the man that is standing over there?
Which is the tool that you are looking for?
(四).不可由that引导的定语从句
1.在非限制性定语从句中。 Mr Smith ,who lives in Chicago, is a doctor .
2.关系代词在从句中作前置介词的宾语时。This is the room in which Mr Liu once lived .
3.由that作先行词时。 The bread which is made by my mother is better than that which is sold in food shops.
4.someone,somebody,nobody,anyone,anybody,everyone,everybody等指物的不定代词作先行词时。Anyone who breaks the law will be punished.
（五）.非限制性定语从句的特点：1.不能用that引导定语从句。2.关系代词不能省略。
（六）关系副词的用法：关系副词代替先行词在定语从句中与相应的介词一起充当状语。
1． When指代表示时间的先行词在定语从句中与相应的介词一起充当时间状语。例如：
October 1，1949 was the day when（=on which） the People’s Republic of China was founded.
2． Where指代先行词在定语从句中与相应的介词一起充当地点状语。例如： We will visit the house where(=in which)Lu Xun was born.
3. why代替先行词在定语从句中与相应的介词一起充当原因状语.例如: Who can tell me the reason why(=for which) Tom was absent today? 状语从句?
1、时间状语从句
（1）as、when、while用法一览表。
类别 作 用 例 句
as 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) while 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 others are working.
He fell asleep while/when reading. Strike while the iron is hot.(用as或when不可，这里的while意思是“趁……”)
（2）引导时间状语从句的连接词除上述外还有：
①till, not … until …, until, before, since
Don’t get off the bus until it has stopped.
He waited for his father until(till)it was twelve o’clock.
It will be five years before he returns from England.
②hardly / scarcely … when, no sooner … than, as soon as once 表示“一……就”
As soon as I have finished it , I’ll give yu a call.
Once you show any fear, he will attack you.
We had hardly got / Hardly had we got into the country when it
began to rain.
No sooner had he arrived / He had no sooner arrived than she started complaining.
③directly, immediately, the moment, the minute that… 一……就 He made for the door directly he heard the knock.
④each time, every time, by the time
Each time he came to my city, he would call on me.
注意：表示未来情况，主句用将来时，从句用现在时。
2、让步状语从句
（1）although与though可以引导让步状语从句，不能与but连用，但可以与yet连用。
Although they are poor,(yet)they are warm-hearted.
（2）even if或even though引导让步状语从句，表示“即使”，“纵然”，用来使人注意下文所强调内容的性质。
I’ll get there even if(though)I have to sell my house to get enough money to go by air.
（3）no matter后接上who、what、where、how等疑问词，也可以在这类疑问词后面加上ever构成whoever、whatever、wherever、however等。 Don’t trust him, no matter what / whatever he says.
Whoever breaks the law will be published.
No matter how hard the work is, you’d better try to do it well.
（4）as也可以引导让步状语从句。要用倒装。
Child as(though)he is, he knows a lot.
Much as I like it, I won’t buy.
Try as he would, he couldn’t lift the heavy box.
3、原因状语从句：because, for, as, since, now that
（1）表示不知道的原因时用because,即说话人认为听话人不知道，因此because从句是全句最重要的部分，通常它被置于主句之后。
You want to know why I’m leaving? I’m leaving because I’m full.
for虽然表示不知道的原因，但其语气较because要弱得多，是可说可不说的话，它只能置于主句之后，这时，for是并列连词。如果不是因果关系，而是对前面主句的内容加以解释或推断时，只能用for。如：It’s morning now, for the birds are singing.（很显然，鸟叫不可能是“现在已是早上”的原因。）
（2）表示已经知道的原因时用as或since,即某种原因在说话人看来已经很明显，或已为听话人所熟悉，因此它是句中不很重要的部分。since要比as正式一些，它们通常被置于语句之前，但有时却相反。
Seeing all of the children already seated, he said,“Since everyone is here, let’s start.”
(3)下列情况下只能使用because:
①在回答why的问句时；
②在用于强调句型时；
③被not所否定时。
4、地点状语从句：where, wherever
Make a mark wherever you have any questions.
We will go where the Party directs us.
5、目的状语从句：that, so that, in order that
注意：目的状语从句的谓语动词常与情态动词连用，否则可能是结果状语从句。不可置于句首。
6、结果状语从句：that, so that, so … that, such … that …
注意：so + 形容词/副词 + that从句；such + 名词 + that从句。
7、方式状语从句：as, as if(though)
I’ll do as I am told to.
It looks as if it is going to rain.
8、比较状语从句：than, as
9、条件状语从句：if, unless, so (as) long as, in case, once, a far as, on condition that.
注意if与unless的区别：不能用and连接两个unless从句，即不能有… unless …,and unless … 。但if … not and if … not却不受此限。
You won’t lose your weight unless you eat less and unless you exercise more.(×)
但可以说 … unless you eat less and exercise more.