让步状语从句
定义：让步状语从句是状语从句中的一种，其本身也是状语从句。一般翻译为“尽管……”或“即使……”，就是我们日常生活中用的“退一步说……”的感觉。
引导让步状语从句的连词主要有：though和although（虽然，纵然），while, as（虽然..但是..）; even if和even though（即使…纵使…）; whether...or...(无论是否或不管是…还是…); no matter+疑问词（不管…都…），疑问词-ever，regardless of+名词/名词短语/名词从句，despite 和in spite of(尽管).
1．although 和though 引导的让步状语从句：
①两个词同义，一般情况下可以互换使用，如：
He didn’t light the fire though / although it was cold.
②although 比though 较正式，语气较重，常用于强调让步概念，如：
He insisted on doing it although I warned him not to.
③though可以和even 连用，但although 不可以，如：
Although (Even though) the traffic held us up, we got to the airport on time.
④当让步状语从句是指一种假设的情况，不指事实时，通常用though，而不用although，如：
Though all the world were against me, I shall still hold to my opinion.
⑤though可以在非正式文体中用作连接性状语，而although 则不行。（though 可以放在句中或句末，通常用逗号隔开），如：
He said he would come; he didn’t, though.
⑥though引导的从句可用倒装语序（即把从句中的表语或状语等放在though之前），而although 不能这样用，如：
Young though she is, yet she is fit for the job. (= Young as she is, …)
⑦有时可用副词yet, still, nevertheless (但不能用连词but) 来配合连接词though或although，以加强语气，如：
Though he is over seventy, yet / still / nevertheless he can ride the bike.
⑧though和although后面的主语和谓语动词be 可以省略，如果这个主语和主句中的主语指同一个人或物时，如：
Though (it was) cold, it was a fine winter morning.
Though (they were) very tired, they continued to march on.
2．even if, even though和if 引导的让步状语从句：
①even if 与even though同义，常用于强调让步概念，如：
I’ll do it, even if it takes me all the afternoon.
Even if you fail, you can try again.
注：if 有时也可以用于让步含义，但要注意条件if 与让步if 的区别，试比较：If he is poor, how can he buy the house? (条件)
If he is poor, he is at least honest. (让步) (= even if)
If John had been there, I would have seen him. (条件)
If John was there, I didn’t see him. (让步) (= even if)
3.由as, that, though引导的特殊让步状语从句结构：
在正式文体或文学作品中，为了强调让步的含义，可用as引导让步从句。但as一般不置于句首，而将从句中的表语或状语置于句首。（though, that与as一样，也可以用于这种结构），如下面几种情况：
①表语的倒装：
Tired as he was, he still went on with his work.
Difficult though the task was, they managed to accomplish it in time.
②状语的倒装：（这时不可在状语之前加very, much等修饰语）
Much as he likes the bike, he doesn’t want to buy it.
Hard as I studied, I could not catch up with them.
③谓语动词的倒装：
Try as he would, he could not remember a word of it. (= No matter how he would try …) Search as they would, they could find nothing in the room.
注意事项：
①如果是单数名词或形容词最高级作表语，不再用冠词，如：
Youngest as he is in our class, he speaks English the best.
②as从句可以置于主句前、主句中或句后，当as从句置于句首时，主句前可加yet ，如：
Rich as he is, (yet) I don’t envy him.
③当作表语的形容词提前时，如果从句的主语是人称代词，那么它只能放在动词之前(半倒装)；如果从句的主语是名词，则可用倒装语序(全部倒装) ，也可用陈述语序，如：Clever though / as you may be, you can’t do that.
Tired as were the workers, they did not stop.
④as 从句与主句在时态上可以不一致，如：
Child as he is, he was brave.
⑤注意区别as 引导的原因从句与让步从句，试比较：
Lawyer as he is, he explains the reason clearly. (原因从句)
Lawyer as he is, he can’t explain the reason very clearly. (让步从句) 4．even though和though
even though (= even if) 引导的从句指把握不大或假设的事情，意为“即使”、“纵然”；though 引导的从句指事实，意为“尽管”、“虽然”，
例如：
He will not reveal the secret, even though he knows it. (可能知道，也可能不知道。)
He will not reveal the secret though he knows it. (虽然知道，却不说出来。)
5．while引导的让步状语从句：
while (= although),它引导的让步状语从句只能前置，位于句首，如：
While you may be right, I can’t altogether agree.
注意比较下列各句：
