提到條件句,人們一般會想到if引導的條件句,而英語中某些假設的條件句不是通過if從句表達出來,而是包含在某些短語、上下文或其他方式中,其謂語也常用虛擬語氣,我們稱此種結(jié)構(gòu)為含蓄條件句.
（人教版）高中教材Book Ⅵ. Unit Ι. Art Page 3,課文最后一段出現(xiàn)了這樣一個句子：“But without the impressionists, many of these painting styles would not exist.”由句意可以看出,此處應是一個條件句,而且暗含虛擬語氣,這里假設的條件沒有通過條件從句表達出來,而是隱含在without介詞短語中,故名含蓄條件句.譯作：但是如果沒有印象派,那么這許多不同的風格就不可能存在.
又例如：Without water, there would be no life. 如果沒有水,就不會有生命.
但可作含蓄條件句的并非without一種,我們就試著找出以下幾種可作虛擬語氣的含蓄條件句,以饗讀者.
Ⅰ. But for the meeting, I would have gone home at the time.
要不是開會,我早就回家了. (but for 暗示了條件)
Ⅱ. It would be only partly right to follow in this way.
如果用這種方式,僅僅對了一半. （動詞不定式暗示了條件）
Ⅲ. Having known in time ,we might have prevented the accident.
要是及時得知的話,我們也許能阻止這場事故.
（-ing 分詞做條件狀語,暗示條件：If we had kown in time）
Ⅳ. Given more attention, the tree could have grown better.
如果多留心的話,這樹本來可以長的更好.（MET 1990）
(-ed 分詞做條件狀語,暗示: If the tree had been given more attention)
Ⅴ.I was too busy at that time, otherwise, I would have called you.
我當時太忙,否則我就給你打電話了.
（副詞otherwise暗示條件）
由此可知,在特定的上下文或一目了然的情況下,if條件句可以省略,或使用介詞短語、副詞或非謂語動詞等形式來代替if條件句,這種虛擬語氣表達形式叫做含蓄條件句
所以,含蓄條件句的本質(zhì)就是隱含if的虛擬語氣句