由下列名詞或短語引導，或含有某些詞的從句中應用的虛擬語氣

1.“Iest 以免、惟恐”引導的從句用“should+動詞原形”。

He took a map with him lest he (should ) lose his wag there.

2.“whether不管、無論”引導的讓步狀語從句，有時用動詞原形。

All things, whether you know or don’ t know, exist in the world.

3.用“would rather/had rather’ would just as soon"表示“寧愿、但愿”，后面的賓語從句謂語用過去式或動詞原形表示對將來的要求，用過去時表示對現在的愿望，用過去完成時表示對過去做的事的懊悔。

Don’ t live in the world, I would rather( I would just as soon) you die.

I would rather you go tomorrow.

I would rather everything hadn’ t happened in the past.

4.用“had hoped”表示原來希望做到而實際上未能實現的事情，其賓語從句的謂語用“would+動詞原形”。

I had hoped that she would go to the U.S. and study there, but she said she liked to stay in China.

5.在“It is(high/about)time+that”引導的定語從句中，定語從句的主謂語用一般過去時，偶爾也可以用would(或should)+動詞原形，或had rather (would rather)+動詞原形。

It is hihg (about)time that we left/should leave/ had better leave/had rather leave/ were leaving.(注意與“This is the first/second…time”后從句中用現在完成時的區別。

6.用“without/but for/in the absence of ”表示“要不是”，“如果沒有”(相當于if it were not for…)表示條件時，句中一般用虛擬語氣。(也可用陳述語氣)

Without your help, I couldn’ t finish my work on time.

In the absence of water and air, nothing could live.

7.由“providing (that)/ provided (that)/on condition that/ in order that”引導的條件從句或目的從句，根據情況，可用虛擬語氣。(有時也可用陳述語氣)

They are willing surrender provided they are given free passage. if ,將were等提到主語前，形成倒裝。

Should there be a good film tomorrow. I would go to the theatre with you.

Were it not for your help. I wouldn’ t be succeed.