一.定義：在復(fù)合句中起主語作用從句

二.結(jié)構(gòu)：關(guān)聯(lián)詞?主語從句剩余部分

三.關(guān)聯(lián)詞：

1.從屬連詞：that, whether

2.連接代詞：who, what, which, wh-ever

3.連接副詞：when, where, how, why, wh-ever

※注意：主語從句放在句首時，整個句子會顯得笨重，為了使句子結(jié)構(gòu)平衡，優(yōu)美，常把主語從句移到后邊，前邊用引導(dǎo)詞"it"做形式主語。

四.it 作形式主語的運用

1.It?is/was?名詞（名詞詞組）?主語從句

It's a fact …

It's a pity …

It's a shame …

It's an honour …

It's a question …? 等等

E.g.

It’s a pity that you missed the exciting football match.

It remains a question whether he will come or not.

2.It?is/was?形容詞?主語從句

It's natural …

It's? obvious…

It's fortunate …

It's possible…

It's unlikely…

3.It?is/was?不及物動詞（vt.）?主語從句

It's seems…

It's happened…

It's appears…

It's possible…

It's turns out…

4.It?is/was?過去分詞?主語從句

It's known…

It's said…

It's reported…

It's decided…

It's announced…

5.其他形式

It doesn't matter…是無關(guān)緊要的

It makes no difderence…毫無區(qū)別

It is of little consquence that…無關(guān)緊要

It suddenly struck me（occurred me）that…

我突然想到…