1.用在虛擬條件句中
虛擬條件句及其主句的謂語形式可歸納如下
從句謂語 主句謂語
與現(xiàn)在事實相反 were, did would (should, could, might) +v
與將來事實相反 should do, would (should, could, might) +v
(可能性極?。?nbsp; were+to+v
與過去事實相反 had done would (should, could, might) + have done
例1:I would certainly go if I had the time.
例2:How nice it would be if you could stay a bit longer.
例3:She would have come if we had invited her.
如果條件從句中包含有were, had, should或could,有時可把if省略掉,但這時要把were, had, should或could放在主語前面(這種結(jié)構(gòu)在口語中較少使用)。例如:
1)Had we made (= If we had made ) adequate preparations, we might have succeeded.
2)Were there no gravity, there would be no air around us.
3)Should it rain tomorrow, the meeting would be put off.