條件句有兩種,一種是真實條件句(Sentences of Real Condition),表示一個可能實現(xiàn)的情況:
I'll help him if he asks me.
如果他向我提出,我可以幫助他。
If she isn't in, leave her a note.
如果她不在家,給她留一個條子。
另一種是虛擬條件句(Sentences of Unreal Condition),表示一種純然假想的情況或實現(xiàn)的可能性不大的情況,這時動詞需用特殊形式,稱為虛擬語氣,虛擬條件句有兩種:
1.談過去的情況,動詞為:had+過去分詞, would have+過去分詞
If he had asked me, I would have helped him.
如果他向我提出了,我就幫助他。(但他沒向我提出)
If she had left five minutes earlier, she would have caught the train.
如果她早五分鐘動身,她就趕上火車了。(但動身晚了)
2.談現(xiàn)在或將求情況,動詞為:過去式would+動詞原型
If I had the money, I would travel round the world
如果我有錢我將作環(huán)球旅行。(但我沒有錢)
I would help you if I could.
如果能我是會幫助你的。(但不可能)
動詞為be時,多用were這個形式:
If I were you, I would accept the job.
我要是你我會接受這份工作。
有時if可以省略,這時后面要用倒裝語序:
Had I taken (=If I had taken) your advice, I wouldn't have made that mistake.
如果我聽了你的勸告,我就不會犯那個錯誤了。
Were I in your position, I would stay.
我要是處在你的地位我會留下。
條件從句 主句
had+過去分詞 would have +過去分詞
條件從句 主句
過去式 would +動詞原形