什麼是從屬連詞

從屬連詞是連詞的一種，用來引導名詞性從句或狀語從句。連詞通常引導一個從句，修飾主句。 由從屬連詞所引導的句子叫從句，而含有從句的句子叫作複合句

·從屬連詞可分為三大類：

1、that （無詞義，不做成分）

if，whether （表達是否的意義，但不做句子成分）

2、連接代詞：who，whom，whose，what，which，whatever， whoever， whichever（有詞義，在句子中可作主語、表語、賓語）

3、連接副詞：when，where，why，how，how many，how long，how far，however，whenever，wherever （有詞義，作從句的狀語）

用法：

從結構上説，英語連接詞分兩大類：並列連詞和從屬連詞。

並列連詞連接兩個或兩個以上地位平等的字、詞組或分句。

例如：

(1) Air and water are indispensable to me.

(2) She likes going out with friends or playing outdoor games.

(3) Most workers have a good income， so they look very happy.

從屬連詞連接兩個或兩個以上的分句，形成複雜句中的從屬分句。

例如：

(4) He said that he did not want to go .

(5) Many things have happened since I last saw him.

(6) You may come if you want to.

從屬連詞用來連接各種從句。

如動詞是持續行動詞，它要用肯定句，如：

I studied hard until 12 o'clock last night.

如果動詞是瞬間截止性動詞，則要用否定句

如:

He didn't go to bed until his mother came back.

由since，for，by，before， 來引導的時間狀語從句。

since 引導的時間狀語是動作的開始時間

如:

I have studied English since 1990.

而by引導的時間狀語通常是動作的結束時間

如：

I had learned 25 English songs by the end of last term.

·