虚拟语气主要用于if条件状语从句，也可用于主语从句、表语从句、宾语从句等。IwishIcouldhelphim.我希望我能帮助他。
虚拟语气概述：虚拟语气表示说话人所说的话不是事实，而是一种假设、愿望、怀疑或推测。虚拟语气主要用于if条件状语从句，也可用于主语从句、表语从句、宾语从句等。
If I had seen him yesterday, I would have told him the news.
我如果昨天见到他的话，就会把这个消息告诉他的。
It is surprising that you (should) not understand me!
太奇怪了，你竟然不理解我！
1.与现在事实相反的虚拟语气,if从句中的谓语用过去式（be用were),主句用would/could/mightshould 动词原形。
If I had enough money, I would buy myself a computer.
我如果有足够的钱，会为自己买一台电脑。
If I were you, I would forgive Mary.
如果我是你，我就会原谅玛丽。
2.与将来事实相反的虚拟语气，从句谓语过去式（be用were)/should 动词原形/were to 动词原形，主句谓语would/could/might/should do.
If I saw/should see/were to see him tomorrow, I would invite him home.
我如果明天见到他，会邀请他到家里来。
If I were to do the job, I would do it in a different way.
要是我来做这项工作，我会用另一种方法。
3.与过去事实相反的虚拟语气，主句谓语should/would/could/might have 过去分词,If 条件从句的谓语形式had 过去分词词。
If we had had enough rain last year,we could have gained a good harvest.
如果去年雨水充足的话，我们可能会有一个好收成。
If the weather had been nice yesterday,we would have gone for a picnic.如果昨天天气好的话，我们就去野餐了。
4. wish后的宾语从句用虚拟语气，从句的谓语形式虚拟情况
与现在事实相反用：过去式（be用were)
与过去事实相反had＋过去分词
与将来事实相反would/ could/might＋动词原形
I wish (that) I were a bird and could fly freely in the sky.
我希望我是一只鸟，可以在天空中自由地飞翔。
I wish(that)I had met that writer.
我希望遇到过那位作家。
I wish I could help him. 我希望我能帮助他。
5.would rather后的宾语从句用虚拟语气虚拟情况表示现在或将来的愿望，从句的谓语形式过去式( be用were),表示过去的愿望,用had＋过去分词
I would rather you came next Saturday.我宁愿你下周六来。
I would rather you had taken the place of me.我宁愿你顶替了我。
6 .as if/as though 引导的虚拟语气
as if/as though引导的虚拟语气谓语的形式与wish后的宾语从句的谓语形式一致。
She talked about the film as if she had really seen it.
她谈论那部影片，就好像她确实看过一样。
It seems as if it were spring already.
现在仿佛已是春天了。
【误区警示】如果与事实相符，as if/as though后的从句用陈述语气。
It looks as if it is going to rain. 仿佛天要下雨。（马上就要下雨）
It seems as if the boy has lost his way,这个男孩好像迷路了。
7.if only...句式用虚拟语气
if only. . 意为“要是······就好了”，其后虚拟语气的用法与wish后的宾语从句的谓语形式一致。
If only I were 20 years younger!
我要是年轻20岁该多好啊！（与现在的事实相反）
If only I had come to the party yesterday!
要是昨天我来参加聚会就好了！（与过去的事实相反）
If only I could fly to the moon one day.要是有天我能飞上月球就好了。（与将来的事实相反）
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