初中英語語法歸納（十一）

He was doing his homework when I came in.（當）我進來時，他正在做家庭作業(yè)

I came in when/while he was doing his homework.當他在做家庭作業(yè)時，我走了進來

While/When I was in the town，I saw him twice.（當）我在城里時，見過他兩次

Strike while the iron is hot．趁熱打鐵。．

when還可譯作這時while還可譯作“而”

He was playing football outside when it began to rain.

他在外面踢足球，這時開始下起雨來。

He is tall while his elder brother is short.

他個子高，而他哥哥個子矮

2. because，since.和as

because引導的從句通常表示說話人認為聽話人不知道的原因或理由，從句往往是整個主從復合句的重心。

He was annoyed because he missed the bus. 他感到為難是因為他沒有趕上那班車

since和as表示原因時，往往表示人們顯然已知的理由或原因；因此，側(cè)重點是主句的內(nèi)容，原因只作附帶說明。在語氣上，becausc最強，since次之（在意義上相當于漢語中的“既然”),as最弱

Since his method doesn‘t work，let‘s try yours. 既然他的方法不起作用，我們就試一試你的。

As she was in a bad mood，we left her alone. 由于她心情不好，我們不去打擾她了。

He is absent frorn school because he is ill. 因為他生病，所以他沒來上課

Because/As it was wet，we went there by bus. 因為下雨，所以我們乘車去那兒。

Since everybody is here，let‘s begin. 既然大家都到了，我們就開始吧。

3.if和unless

引導條件狀語從句的連詞，主要是if和unless,由if條件狀語從句可以是真實的條件句，也可以非真實條件句．真實條件句所表示的條件指的是事實，即可以是實現(xiàn)的事，非真實條件句指的是與事實相反或不大可能實現(xiàn)的事．

If it rains, the match will be cancelled（取消）． 如果天下雨，比賽將被取消

If I were you, l should consult（請……看病）a doctor. 我要是你，我就去看醫(yī)生

If I had tried hard last term，I would have succeeded. 如果上學期我努力的話，我現(xiàn)在就已經(jīng)成功了

unless在意義上相當于if... not

You will fail unless you work harder. 除非你努力，否則你不會成功。