類別

用法

例句

If引導的條件從句

與現(xiàn)在事實相反

從句動詞：過去式（be用were）

主句動詞：should/would/could/might+動詞原形

If he were here, he would help us.

與過去事實相反

從句動詞：had+過去分詞

主句動詞：should/would/could/might+have+過去分詞

If I had been free, I would have visited you.

與將來事實相反

從句動詞：過去式/ should+動詞原形/ were+不定式

主句動詞：should/would/could/might+動詞原形

If it should rain tomorrow, we would not go camping.

其它狀語從句

as if引導的狀語從句中動詞用過去式或過去完成式

They are talking as if they had been friends for years.

in order that / so that引導的狀語從句中動詞用can / could / may / might / would等+動詞原形

Turn on the light so that we can see it clearly.

賓語從句

demand, suggest, order, insist后接的從句中動詞為should+動詞原形

He suggested that we not change our mind.

wish后的從句中分別用過去式，過去完成式和should/would+動詞原形表示與現(xiàn)在，過去和將來情況相反

I wish I could be a pop singer.

主語從句

在It is necessary / important / strange that…, It is suggested / demanded / ordered / requested that… 等從句中，謂語動詞用should+動詞原形

It is strange that such a person should be our friends.

其它句型中

It is time that…句型中動詞用過去式或should+動詞原形

It’s high time that we left.

would rather所接的從句中動詞用過去式或者過去完成式

I would rather you stayed at home now.

If only句型中動詞常用過去式或者過去完成式，表示強烈的愿望

If only our dream had come true!