狀語從句，條件狀語從句，比較狀語從句，目的狀語從句，結果狀語從句和讓步狀語從句等。由連接詞if引導的狀語從句叫做條件狀語從句。（註意：在含有條件狀語從句的復合句中，如果主句是壹般將來時態，從句要用壹般現在時[主將從現原則])
語法
經典語句：If it dosen't rain tomorrow,we will go to the zoo.
If you open the door，i will come in.
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
連接詞主要有 if, unless, as/so long as, on condition that,provided,suppose,supposing 等。.
主句用壹般將來時，if或unless引導的條件狀語從句用壹般現在時。
固定搭配：unless = if...not.
e.g. Let's go out for a walk unless you are too tired.
If you are not too tired, let's go out for a walk.
if 引導的條件句有真實條件句和非真實條件句兩種:
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壹種，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
由as (so) long as, in case引導。
So long as you’re happy, it doesn’t matter what you do.
只要妳高興，妳做什麽都沒有關系。
You may borrow my book as long as you keep it clean.
只要妳保持書的清潔，妳就可以把我的書借去。
Take your umbrella in case it rains.
帶著妳的傘吧，以防下雨。