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.
注：如果条件从句中包含有were, had, should或could，有时可把if省略掉，但这时要把were, had, should或could放在主语前面(这种结构在口语中较少使用)。
1)Had we made adequate preparations, we might have succeeded.
Had we made = If we had made
2)Were there no gravity, there would be no air around us.
3)Should it rain tomorrow, the meeting would be put off.
这种用法也常见于or, or else, otherwise和but后面的分句中。
1)Without music, the world would be a dull place.
2)But for your help, we would have failed.
3)She would have gone with us, but she didn’t have time.
4)He must have had an accident, or he would have been here then.
1)If you hadn’t watched television so late, you wouldn’t be so sleepy now.
2)If you were in better health, we would have allowed you to join them in the work.
1)I wish I had learned to play chess.(与过去事实相反)
2)I wish I remembered his address.(与现在事实相反)
3)I wish he would try again.(对将来情况的假设)
1)I wish you would help us.
2)I wish you would stop asking such silly questions.
1)If only I knew what you wanted.
2)If only you hadn’t told him what I said, everything would have been all right.
6.用在以as if (as though) 引出的方式状语从句中
1)The old couple loved the orphan girl as if she had been their daughter.
2)It seems as if it were spring.
例1：He was the very person I should have been wished to see.
例2：It’s (high) time that we went to class.
例1：I’d rather they came tomorrow.
例2：He’d rather I went to Fuzhou by sea.
例3：I’d just as soon you didn’t watch television this evening.
但had rather, would rather, would just as soon, would sooner等惯用语如用在简单句中，其后都用不加to的动词不定式。
1)I’d rather die than give up my principle.
2)I’d just as soon (would sooner) resign than take part in such dishonest deals.
1. should +动词原形(有时省略should)
(1)用在动词如advise, command, demand, desire, insist, order, propose, recommend, request, require, suggest, urge等后的宾语从句中。
1)They requested that we (should) send a delegation to their country.
2)She urged that he write and accept the post.
(2)用在it is suggested, it is desired, it is required, it was ordered, it was proposed, it has been decided, it is necessary (essential, imperative, important, desirable) that等引出的主语从句中。
1)It is desired that we (should) get everything ready by tonight.
2)It is necessary that the teacher (should) have a thorough knowledge of the subject he teaches.
(3)用在suggestion, motion, proposal, order, recommendation, plan, idea, requirement等引起的表语从句和同位语从句.
例如：He put his coat over the child lest he should catch cold.
例如：They talked as if they had been friends for years.
例如：It is high time you handed in your test paper.
例1：I wish I were as strong as you.
例2：He insisted that we (should) take up the matter at the meeting.
例1：Could you spare me a few minutes?
例2：You might have told me earlier.
例3：Hadn’t you better go and see you dentist about that tooth?
例1：Long live world peace.
例2：May you succeed.