高中英語語法
一、表語從句
1.定義：用作表語的從句叫做表語從句。
2.構成：關聯詞+簡單句
3.引導表語從句的關聯詞的種類：
(1)從屬連詞that。如：The trouble is that I have lost his address.麻煩是我把他的地址丟了。
(2)從屬連詞whether,as,as if。如：He looked just as he had looked ten years before.他看起來還與十年前一樣。
注：從屬連詞if一般不用來引導表語從句，但as if卻可引導表語從句，如：All this was over twenty years ago,but it's as if it was only yesterday.這都是20多年前的事了，但宛如昨天一樣。能跟表語從句的謂語動詞一般為系動詞be,seem,look等。
(3)連接代詞who,whom,whose,what,which,whoever,whatever,whichever 連接副詞 where,when,how,why。如：The problem is who we can get to replace her.問題是我們能找到誰去替換她呢。
解釋：連詞because可引導表語從句。如：I think it is because you are doing too much.我想這是因為你做得太多。在一些表示“建議、勸說、命令”的名詞后面的表語從句中，謂語動詞用虛擬語氣。should+動詞原形表示，should可省略。如：My suggestion is that we (should)start early tomorrow.我的建議是我們明天一早就出發(fā)。
二、主語從句
1.定義：用作主語的從句叫做主語從句。
2.構成：關聯詞+簡單句
3.引導主語從句的關聯詞有三類：
(1)從屬連詞that。如：That they were in truth sisters was clear from the facial resemblance between them.很明顯，她們確是親姐妹，她們的臉型很相似。
(2)從屬連詞whether。如：Whether he’ll come here isn’t clear.他是否會來這里還不清楚。
(3)連接代詞who,whom,whose,what,which,whoever,whatever,whichever 連接副詞 where,when,how,why。如：What she did is not yet known.她干了什么尚不清楚。
三、賓語從句
1.定義：用作賓語的從句叫賓語從句。
2.構成：關聯詞+簡單句
3.引導賓語從句的關聯詞有三類：
(1)從屬連詞that。如：He told us that he felt ill.他對我們說他感到不舒服。I know he has returned.我知道他已經回來了。注：that在引導賓語從句時也并不是任何情況下都可以省略。在以下情況下，that不能省略。
1.Everybody could see what happened and that Tom was frightened.(and連接兩個賓語從句，that賓語從句放在and的后面時，that不能省略。)大家都會看出所發(fā)生的事情并知道Tom非常害怕。
2.I know nothing about him except that he is from the south.(that引導的賓語從句作介詞賓語時，that不能省略。)對他我一無所知，只知道他是南方人。
3.That he ever said such a thing I simply don’t believe.(that從句位于句首時，that不可省略。)我簡直不相信他曾說過這樣的話。
4.We decided,in view of his special circumstances,that we would admit him for a probationary period.(主句謂語動詞與that從句之間有插入語，that不可省略。)鑒于他的特殊情況，我們決定應允他一段試用期。
(1)介詞賓語從句 賓語從句也可用作介詞的賓語。如：He was deeply displeased by what had occurred that day.他對那天發(fā)生的事感到很不快。
(2)從屬連詞if/whether。如：I doubt whether he will succeed.我懷疑他是否會成功。I don’t know if you can help me.我不知道你能否幫助我。
(3)連接代詞who,whom,whose,what,which,whoever,whatever,whichever 連接副詞 where,when,how,why。如：Who or what he was,Martin never learned.他是什么人?他是干什么的?馬丁根本不知道。
四、同位語從句
1.定義：用作同位語的從句叫做同位語從句。
2.用法：同位語從句的先行詞多為fact,news,idea,thought,question,reply,report,remark等，關聯詞多用從屬連詞that。如：They were all very much worried over the fact that you were sick.對你生病這件事，他們都很焦慮。
注：同位語從句偶爾由從屬連詞whether引導。如：I have no idea whether he’ll come or not.我不知道他是否來。
連接代詞who,which,what和連接副詞where,when,why,how亦可引導同位語從句。
五、不定式的構成
不定式是由不定式符號to+動詞原形構成，在某些情況下to也可省略。
不定式的一般式所表示的動作通常與主要謂語的動作同時或幾乎同時發(fā)生，或是在它之后發(fā)生。如：They invited us to go there this summer.他們邀請我們今年夏天去那兒。