連線詞主要有 if, unless, as/so long as, on condition that 等..
if 引導的條件句有真實條件句和非真實條件句兩種.
主句用一般將來時,if或unless引導的條件狀語從句用一般現在時.
固定搭配
unless = if not.
Let"s go out for a walk unless you are too tired.
If you are not too tied, let"s go out for a walk.
真實條件句,
如：If it rains tomorrow, we won”t go on a picnic.
非真實條件句是虛擬語氣的一種,表示與事實相反,如：
If I were you, I would go with him.
if wrless,on condition that
so/as long as只要
時間狀語從句
時間狀語從句
（adverbial clause of time）
1.由when, while, as引導的時間狀語從句.例如：
When you think you know nothing, then you begin to know something.當你以為自己一無所知的時候,你就是在開始知道一些事物了.
When truth is buried under the ground it grows, it chokes, it gathers such an explosive force that on the day it bursts out , it blows up everything with it.當真理被埋在地下的時候,它在生長,它感到壓抑,它蓄存著這麼一種爆炸性力量,一旦冒出,它就會炸破一切!
Strike while the iron is hot. 趁熱打鐵.
Will you watch my clothes while I have a swim. 我游泳的時候,請你照看一下我的衣服.
You can feel the air moving as your hand pushes through it. 當你的手在空氣中揮動的時候,你就能感覺到空氣在流動.
條件狀語從句
條件狀語從句就是用以表示“在某種條件下,會……”
常用if ,in case , on condition等詞來引導
連線詞主要有 if, unless, as/so long as, on condition that 等..
if 引導的條件句有真實條件句和非真實條件句兩種.
主句用一般將來時,if或unless引導的條件狀語從句用一般現在時.
固定搭配
unless = if not.
Let"s go out for a walk unless you are too tired.
If you are not too tied, let"s go out for a walk.
真實條件句,
如：If it rains tomorrow, we won”t go on a picnic.
非真實條件句是虛擬語氣的一種,表示與事實相反,如：
If I were you, I would go with him.
if wrless,on condition that
so/as long as只要
時間狀語從句
時間狀語從句
（adverbial clause of time）
1.由when, while, as引導的時間狀語從句.例如：
When you think you know nothing, then you begin to know something.當你以為自己一無所知的時候,你就是在開始知道一些事物了.
When truth is buried under the ground it grows, it chokes, it gathers such an explosive force that on the day it bursts out , it blows up everything with it.當真理被埋在地下的時候,它在生長,它感到壓抑,它蓄存著這麼一種爆炸性力量,一旦冒出,它就會炸破一切!
Strike while the iron is hot. 趁熱打鐵.
Will you watch my clothes while I have a swim. 我游泳的時候,請你照看一下我的衣服.
You can feel the air moving as your hand pushes through it. 當你的手在空氣中揮動的時候,你就能感覺到空氣在流動.
Our headmaster laughed as she spoke.我們的校長邊談邊笑.
【區別】when, while和as的區別：when引導的從句的謂語動詞可以是延續性的動詞,又可以是瞬時動詞.並且when有時表示“就在那時”.例如：
When she came in, I stopped eating.她進來時,我在吃飯.(瞬時動詞)
When I lived in the countryside, I used to carry some water for him.當的住在農村時,我常常為他擔水.（延續性的動詞）
We were about to leave when he came in.我們就要離開,就在那時他進來了.
While引導的從句的謂語動作必須是延續性的,並強調主句和從句的動作同時發生（或者相對應）.並且while有時還可以表示對比.例如：
While my wife was reading the newspaper, I was watching TV. (was reading是延續性的動詞,was reading和was watching同時發生)
I like playing football while you like playing basketball.我喜歡踢足球,而你喜歡打籃球.（對比）
As表示“一邊……一邊”,as引導的動作是延續性的動作,一般用於主句和從句動作同時發生；as也可以強調“一先一後.例如：
We always sing as we walk.我們總是邊走邊唱.（as表示“一邊……一邊”）
As we was going out, it began to snow.當我們出門時,開始下雪了.（as強調句中兩個動作緊接著先後發生,而不強調開始下雪的特定時間）
2.由before和after引導的時間狀語從句.注意before引導的從句不再用否定式的謂語,並且當before引導的從句位於主句之後,有時譯成“就,才”.還要注意主句和從句之間的時間關係.當主句用將來時,從句總是用現在時；如果before引導的從句謂語用的是過去時,則主句動詞多用過去完成時,這樣以便體現動作發生的先後.After表示主句動作發生在從句動作之後.主句和從句的動作的時間關係正好與before引導的從句相反.例如：
It will be four days before they come back. 他們要過四天才能回來.
Einstein almost knocked me down before he saw me.愛因斯坦幾乎把我撞倒才看到我.