Now that you have come, you may as well stay.

Seeing (that) he is inexperienced, he is not fit for the job.

I often go to the concert for the simple reason that I love music.

I like the city, but I prefer the country in that there’s fresher air.

Ø         在回答用Why提问的句子和强调句型（It is ... that）时，一般只用because，因为在这些连词中， 

because 最强调原因，而since, as, now that以及并列连词for所讲的原因，要么是双方都已经知道的原因，要么并不是直接原因。

Ø         辨析：because, since, as, for

a.       because是从属连词，意为“因为”，表示造成某种情况的直接原因，语气最强，常用来回答why引导的问句。

---  Why didn’t you come to my birthday party?

---  Because I was too busy.

b.       since, as往往表示众所周知的原因，常译为“既然， 由于”。since从句通常位于主句之前，其语气比as稍强。

Since you come, wait for more time please.

c.        as表示原因时，语气比because和as都弱，引导的从句位于主句前后均可。

As she has no car, she can’t get there easily.

d.       for是并列连词，语气最弱，对前面的分句加以解释或表示推断的原因，多用于书面语中。

I stopped to rest, for I was very tired.

The days are short, for it is now December.

3）   让步状语从句

让步状语从句的连接词有al)though, as, while, even if/though, however, whatever, no matter…, whether… or等。

①      though与although的用法

although和though意义一样，都作“虽然、即使”解，一般情况下可以互换使用，although的语气较重，大多置于句首；though/although引导的让步从句时，主句若用yet或still引出，更强调对比性，但不可出现but.

Although he was Japanese, he spent most of his life in China.

Though it’s hard work, I enjoy it. 尽管是个苦差事，我喜欢。

Ø         表示 “然而”时是副词（用在句尾），用逗号隔开：

e.g. He promised to phone. I heard nothing, though. 他答应打电话的，然而我什么也没听到。

②      even though/even if引导的让步状语从句

两个短语表示语气更强的让步，意为“即使”。

She insisted on her own opinion even though/even if she was wrong.

③      as引导的让步状语从句

as引导的让步状语从句必须以部分倒装的形式出现，被倒装的部分可以是表语，状语，或动词原形。倒装时若带有冠词的名词，冠词需要省去。其词序为：adj./adv./n. /v.+ as +S + V

eg.: Child as/though he is, he knows what is the right thing to do.

Hard as/though he works, he makes little progress.

Try as you may, you can’t succeed without others’ help.

④      whether…or…/ whether…or not引导的让步状语从句

whether…or…/ whether…or not引导的让步状语从句, 意为“不论…是否； 不管是…还是…”.

You’ll have to attend the meeting whether you’re free or not.

Whether you believe it or not, it’s true.

Ø         be＋主语＋or连接的两个表语。这个句型相当于whether…or…引导的让步从句。

e.g.   Be it cheap or dear, I will take it. = Whether it is cheap or dear, I will take it.

⑤      wh-ever引导的让步状语从句

在英语中wh-ever引导的让步状语从句，时常可以换成“no matter + 相应的wh-词”。

Whatever happened, he would not mind.

  = No matter what happened, he would not mind.

    I’ll wait for you however late it is.

  = I’ll wait for you no matter how late it is.

Ø         “no matter+疑问词”的结构只能引导让步状语从句，而wh-ever类词还可以引导名词性从句。

    Whatever (=No matter what) you say, I won’t believe you.

    I’ll eat whatever (≠no matter what) you give me.

    Whoever (≠No matter who) comes will be welcome.

4）   条件状语从句

引导条件状语从句的常用词有if, unless, as/s