1) 時間狀語從句
時間狀語從句主要由以下連詞引導：when, whenever, as, while, since, until, till, before, after, as soon as, once, hardly (scarcely) …when, no sooner …than。
I will discuss the matter with you when we meet tomorrow.
時間狀語從句還可由某些可充當連詞的名詞(the moment, the instant, every time,等)和副詞(instantly, directly等)引導：
I will tell you the news the instant I know.
Note:
①before除了可表示「在…之前」外，還可用來強調主句所表達的時間、距離很長或花費的力量相比較大，可譯為「…才」。(「not …before」可用來強調主句所表達的時間、距離很短或花費的力量相比較小，可譯為「…就」)。
It was a long time before I got to sleep again.
②如果位於when引導的分句之前的主句使用過去進行時、過去完成時或「was/were about to, was/were on the point of」等結構時，when表示突然發生某事，可譯為「正在…突然」或「剛…就」等。這時，不能夠用as或while來代替when。
I was walking on the street when I ran into my old friend John.
2) 條件狀語從句
條件狀語從句主要由以下連詞引導：if, unless, providing/provided (that), suppose/supposing (that), on condition (that), as/so long as, in case等。
So long as you work hard, you will surely achieve good results in examinations.
3) 讓步狀語從句
讓步狀語從句主要由以下連詞引導：though, although, even if, even though, whatever, however, whoever, wherever, no matter how/ what/ where/ when等。以下介紹幾種較特殊的讓步狀語從句。
(1)while引導的讓步狀語從句多放在句首，while相當於although，表示「儘管」，「雖然」。
While I admit I did it, I didn’t intend to.
(2)短語「even now/then/so」相當於「though it is/was true」，表示「儘管如此」，「儘管這樣」。
The fire was out, but even so, the smell of smoke was strong.
(3) as引導的讓步狀語從句要倒裝。
Child as he was, he could speak four languages.
4) 比較狀語從句
比較狀語從句主要由以下連詞引導：(not) as …as, (not) the same as, (not) such …as, not so …as, than, the + 比較級…, the +比較級…等。
We have had a lot more rainfall this year than we had last year.