虛擬語(yǔ)氣（Subjunctive Mood）用來(lái)表示說(shuō)話人的愿望、請(qǐng)求、意圖、建議、懷疑、設(shè)想等未能或不可能成為事實(shí)的情況，以及在說(shuō)話人看來(lái)實(shí)現(xiàn)可能性很小的情況。由于虛擬語(yǔ)氣是動(dòng)詞的一種特殊表現(xiàn)形式，因而動(dòng)詞的變化形式體現(xiàn)出虛擬語(yǔ)氣所包含的不同含義。
虛擬語(yǔ)氣用于非真實(shí)條件句時(shí)的構(gòu)成如下表所述：
If從句
主句
與現(xiàn)在事實(shí)相反
動(dòng)詞的過(guò)去式（be為were）
would（should）＋動(dòng)詞原形
與過(guò)去事實(shí)相反
動(dòng)詞的過(guò)去完成式
would （should, could, might）+ have +動(dòng)詞的過(guò)去分詞
與將來(lái)時(shí)間相反
1）動(dòng)詞的過(guò)去式（be為were）
2）were +不定式
3）should＋動(dòng)詞原形
would (should, could, night)+動(dòng)詞原形
例句：
If I had time, I would go to the movies with you.
If we hadn’t made adequate preparations, the conference wouldn’t have been so successful.
If it were to rain tomorrow, the game would be put off.
虛擬語(yǔ)氣用于非真實(shí)條件句時(shí)的構(gòu)成如下表所述：
If從句
主句
與現(xiàn)在事實(shí)相反
動(dòng)詞的過(guò)去式（be為were）
would（should）＋動(dòng)詞原形
與過(guò)去事實(shí)相反
動(dòng)詞的過(guò)去完成式
would （should, could, might）+ have +動(dòng)詞的過(guò)去分詞
與將來(lái)時(shí)間相反
1）動(dòng)詞的過(guò)去式（be為were）
2）were +不定式
3）should＋動(dòng)詞原形
would (should, could, night)+動(dòng)詞原形
例句：
If I had time, I would go to the movies with you.
If we hadn’t made adequate preparations, the conference wouldn’t have been so successful.
If it were to rain tomorrow, the game would be put off.