1）though， although引导的让步状语从句，后面的从句不能有but，但是 though 和yet可连用。例如：

　　Although it's raining， they are still working in the field.　虽然在下雨，但他们仍在地里干活。

　　He is very old， but he still works very hard. 虽然他很老了，但仍然努力地工作。

　　Though the sore be healed， yet a scar may remain. 伤口虽愈合，但伤疤留下了。（谚语）

　　2）  as， though 引导的让步从句必须表语或状语提前（形容词、副词、分词、实义动词提前）。例如：

　　Child as /though he was， he knew what was the right thing to do. 虽然是个小孩，该做什么不做什么，他全知道。

　　3）  ever if， even though　即使。例如：

　　We'll make a trip even though the weather is bad. 即使天气不好，我们也要去远足。

　　4）  whether…or…　不管……都。例如：

　　Whether you believe it or not， it is true. 信不信由你，这确实是真的。

　　5）　"no matter +疑问词" 或"疑问词+后缀ever" .例如：

　　No matter what happened， he would not mind. =Whatever happened， he would not mind. 不管发生什么，他不在意。

　　替换：no matter what = whatever

　　no matter who = whoever

　　no matter when = whenever

　　no matter where = wherever

　　no matter which = whichever

　　no matter how = however

　　注意：no matter 不能引导主语从句和宾语从句。

　　（错）No matter what you say is of no use now.

　　（对）Whatever you say is of no use now. 你现在说什么也没用了。（Whatever you say是主语从句）

　　（错）Prisoners have to eat no matter what they're given，

　　（对）Prisoners have to eat whatever they're given.囚犯们只能给什么吃什么。