在學習名詞性從句之前，我們首先要明白一個詞：復合句
什么叫復合句
? ? ?由一個主句和一個或一個以上的從句構成的句子叫復合句。在復合句中主句是全句的主體，從句是全句的一個成分，不能獨立。從句通常是用關聯(lián)詞來引導的。在這里關聯(lián)詞還起聯(lián)系從句和主句的作用。?
一、從句的種類：
? ? ?主語從句、賓語從句、表語從句、同位語從句，定語從句和狀語從句
二、名詞性從句的連接詞
1. 單純連詞
在從句中不補充當任何成分，只起到連接從句的功能。
that 沒有實際意義，而whether/ if 在句子中表示“是否” 的意義。
Eg : That the prices of rice will go up is certain. (that引導主語從句，補充當任何成分)
? ? ? ?He asked if I could come to see him this weekend.
? ? ?形式主語it 代替主語從句位于句首時，常見的幾種情況：
? ? ?①?It + adj +that 從句(大多數(shù)情況下that從句后用should+動詞原形)
? ? ? Adj: necessary ?right ?clear ?unlikely ?strange ?obvious ?natural ?important
? ? ? Eg: It is necessary to learn English well.
? ? ? ②?It +系動詞+名詞+that 從句
? ? ? Non: a pity ?an honor ?good news ?a wonder ?a fact ?no wonder ?no surpeise
? ? ? Eg: It is a fact that you are a good boy.
? ? ? ③ It +be + 過去分詞+that從句
? ? ? 過去分詞：said / heard/ reported/ told/ decided/suggested/thought/considered/ hoped/ announced?
? ? ? Eg: It is announced that the plan has been canceled.
? ? ?注意：
? ? ?It + be+ suggested/ advised/ ordered/ requested/ insisted/ demand+ that從句， that從句要用should +動詞原形，should可以省略。
? ? ?Eg: It is suggested that you (should ) spend more time in studying English .
? ? ?當suggest表示“表明”時，不可以用虛擬語氣
? ? ?Eg: It suggests that you are an honest boy.
? ? ?Insist 表示“堅持某種說法（事情已經(jīng)發(fā)生過了）”，不用虛擬語氣。
? ? ?表示“堅持要做（事情沒有發(fā)生）”，要用虛擬語氣。
? ? ?Eg: she insisted that I have never done such thing .
? ? ? ? ? ?She insisted that I study abroad.
? ? ?④It +動詞（+賓語或狀語）+that 從句
? ? ?動詞如： appear(顯得)/ happen(碰巧)/ matter(重要)/ occur(出現(xiàn))/ turn out(結果是)
? ? ?Eg: It happened to me that I was away when he came.主語從句不可位于句首的五種情況：
? ? ?注意：
? ? ?（1）if 引導的主語從句不可居于復合句句首。
? ? ?（2）It is said /reported?結構中的主語從句不可提前。
? ? ? ?正確表達：It is said that President Jiang will visit our school next week.
? ? ? ?錯誤表達：That President Jiang will visit our school next week is said.
? ? ?（3）It happens/occurs?結構中的主語從句不可提前。
? ? ? ?正確表達：It occurred to him that he failed in the examination.
? ? ? 錯誤表達：That he failed in the examination occurred to him.
? ? ?（4）It doesn’t matter how/whether ?結構中的主語從句不可提前。
? ? ? ?正確表達：It doesn’t matter whether he is wrong or not.
? ? ? ?錯誤表達：Whether he is wrong or not doesn’t matter.
? ? ?（5）含主語從句的復合句是疑問句時，主語從句不可提前。
? ? ? ?正確表達：Is it likely that it will rain in the evening?
? ? ? 錯誤表達：Is that will rain in the evening likely?