(1)表示现在的假设(indicating the present unreal consequence)[would+v]：If I were you，I～n't worry too much.如果我是你，我不会太焦虑。If he came， I～n't be surprised. 如果他来，我不会惊讶。 What～you do if you won a million pounds? 如果你赢了百万英镑，你怎么办? Did he sleep，I～wake him up. 要是他睡了，我就把他叫醒。He～if he could. 如果他能办，他会办的。A picnic～n't be any fun without you. 没有你，野餐就没有意思了。W～n't it be simpler to chop it down? 把它砍掉不是更简单吗?She'd be a fool to do it. 她要是干，那她就是个傻瓜。

(2)表示过去的假设(indicating the past unreal consequence)[would +have+pp]：If you had asked，he～have apologized. 如果你要求了，他也许会向你道歉。Had I seen the advertisement I～have applied for the job. 我要是看见了广告，就会申请那份工作了。But for our luck，we～have been dead. 要不是幸运，我们也许早就没命了。I～have preferred to stay at home. 我本来是要待在家里的。I～n't have thought it possible. 我本来会想到这是不可能的。Denial/Refusal～have been useless.否认/拒绝也没有用。

(3)用以提出客气的请求、邀请(used to make polite requests or invitation)：W～you tell her that her boy friend phoned/lend me your pencil? 请你告诉她她的男友来过电话好吗?/请借给我你的铅笔好吗? W～you hold this for me，please? 请您给我拿着好吗? W～you like to come/see the movie? 你愿意来/看这部电影吗? Put the light on，Tom，～you? 汤姆，打开电灯好吗?

(4)表示看法、评论(showing an opinion or idea or giving comments on sth)：I～imagine the trip will take about an hour. 我猜想这次旅途大概需要一个小时左右吧。I think you'd agree/mind my going. 我以为你会同意的/介意我走的。I felt confident that everything～be all right. 我肯定一切都会顺利的。You～expect it to be finished，～n't you? 你期待它会完成，对吗? There were more than one who～have expected. 不只一个人期待过。That's just what he～say/think. 他就是爱说这种话/这么想。That's exactly like him — he～lose the key! 那就是他，总是丢钥匙!

(5)表达意愿(showing one's preferences)(与like、love、prefer、hate、be glad/happy等连用)：I'd love/like a coffee. 我倒想喝杯咖啡。I'd hate you to think I were a fool. 我可不愿意让你觉得我是个傻瓜。I'd be only too glad to help. 我非常愿意帮忙。

(6)表示猜测或能力(indicating imagination or ability of sth)：That～be last month/his father，I think. 我想那是上个月的事/他的父亲。I thought you～have finished it by now. 当时我想你到现在可能就干完了。The door～n't open. 门就是打不开。The wound～n't heal. 伤口就是不愈合。It just～n't bolt on. 它就是插不上。

would that 但愿：W～that we had seen him before he died. 他死之前我们要是见他一面该有多好。I～/W～that I were you! 但愿我是你! 〖同〗wish，hope