时间状语从句
She came up as I was cooking.(同时)
The runners started as the gun went off.(几乎同时)
when：(at or during the time that )既可以表示在某一点的时候，又可表示在某一段时间内，主句与从句的动作或事情可以同时发生也可以先后发生。
It was raining when we arrived.(指时间点)
When we were at school， we went to the library every day.(在一段时间内)
while意思是"当……的时候"或"在某一段时间里"。主句中的动作或事情在从句中的动作或事情的
进展过程中发生，从句中的动词一般要用延续性动词。在when表示a period of time时，两者可以互换。
Please don´t talk so loud while others are working.
He fell asleep while/when reading. Strike while the iron is hot.(用as或when不可，这里的while意思是"趁……")
(2)引导时间状语从句的连接词除上述外还有：
①till， not … until …， until， before， since
Don´t get off the bus until it has stopped.
He waited for his father until(till)it was twelve o´clock.
It will be five years before he returns from England
(1)although与though可以引导让步状语从句，不能与but连用，但可以与yet连用。
Although they are poor，(yet)they are warm-hearted.
(2)even if或even though引导让步状语从句，表示"即使"，"纵然"，用来使人注意下文所强调内容的性质。
I´ll get there even if(though)I have to sell my house to get enough money to go by air.
(3)no matter后接上who、what、where、how等疑问词，也可以在这类疑问词后面加上ever构成whoever、whatever、wherever、however等。
Don´t trust him， no matter what / whatever he says.
Whoever breaks the law will be published.
No matter how hard the work is， you´d better try to do it well.
(4)也可以引导让步状语从句。要用倒装。
Child as(though)he is， he knows a lot.
Much as I like it， I won´t buy.
Try as he would， he couldn´t lift the heavy box.