If引导的条件状语从句
很多英语学习者都觉得If引导的条件状语从句这个句型很难，学习起来很吃力。下面是我为你整理的If引导的条件状语从句的相关资料，希望大家喜欢!
If引导的条件状语从句用法
1.if引导的条件状语从句可以放在主句之前，也可以放在主句之后，如果放在主句之前，中间要用逗号将主句和从句隔开。
例如：
If I am free, I will come to see you.
= I will come to see you if I am free.
如果我有空，我就来看你。
2. 在含if引导的条件状语从句的复合句中，主句用一般将来时，从句通常用一般现在时态表示将来意义，即“主将从现”原则。
例如：
If it snows tomorrow, we will go skiing.
如果明天下雪，我们就去滑雪。
3. 在含if引导的条件状语从句的复合句中，语句的谓语还可含有情态动词can、must、may等，主句也可是祈使句。
例如：
If it stops raining, we can go out.
如果雨停了，我们就能出去。
4. 在含if引导的条件状语从句的复合句中，如果主句部分描述的是客观事实或真理，要用一般现在时。
例如：
If you heat the ice, it turns into water.
如果你加热冰，它就会变成水。
if引导的非真实条件句
对过去的虚拟
条件从句(if):主语+had done 主句might/would/should/could+have done
对现在的虚拟
if+ 主语+动词过去式(be用were)主句 might/would/should/could+do
对将来的虚拟
if+主语+动词过去式(be用were)或主语+should do或主语+were to do
主句 might/would/should/could+do
e.g.
Tom got to the station in time because he started earlier.
If Tom had started late, he would have missed the train.
Do you think the thief entered through the door?
No, if he had, I don't believe, he would have broken the living room window.
If the book weren't so expensive, I would buy it.
If you didn't live so far away, we would be able to visit you more.
What would you do if you lost your passport in a foreign country?
Why hasn't he come? If he should not come on time, we would have to put off the trip.
2.注意事项
e.g.
If she hadn't work hard at English in the past, she wouldn't work as well as a secretary in a large company now. 混合时间的虚拟语气 从句为对过去的虚拟，主句是现在。
Had we not used an out-of-date timetable, we wouldn't have missed the train.
if引导从句的倒装从句相当于 if we had not used an out-of-date timetable, 同样，were还有should 在从句中都可以提前，省略if.
If only 要是...就好了
If only I were younger!
If only I had worked harder in my teenage years!
If only I should travel tomorrow!
虚拟语气的十大句型
一、虚拟条件句：
条件状语从句是非真实情况，在这种情况下要用虚拟语气。
1.条件从句与现在事实不一致，其句型为：
句型1：If +主语+过去时，主语+ should (could, would, 或might) +动词原形
(1) If I were you, I would study hard.
(2) If it rained, I would not be here now.
2.条件从句与过去事实不一致，其句型为：
句型2：If +主语+had+过去分词，主语+ should(could, would, 或might)+ have +过去分词
(3) If the doctor had come last night, the boy would have been saved.
(4) If I had not studied hard, I would have failed in the exam last term.
3.条件从句与将来事实不一致，其句型为：
句型3：If +主语+过去时/ should +动词原形/ were to+动词原形，主语+ should (could, would, 或might) +动词原形
(5) If it should rain tomorrow, we would stay at home.
(6) If I were to go to the moon one day, I could see it with my own eyes.
(7) If you missed the film tonight, you would feel sorry.
注意问题：
1.If条件句中绝对不可以出现would。
2.根据句中的时间状语，有时可能出现“混合虚拟”的情况，即主句可能是现在的情况，条件句也许是发生在过去的情况，但都要遵守上述句型。如：
(8) If you had studied hard before, you would be a college student now and you would graduate from a college in four years’ time.
3.条件句中如果出现were, had, should可省去if，将主语与这些词倒装。例如：
(9) Had the doctor come last night, the boy would have been saved.
(10) Were I to go to the moon one day, I would see it with my own eyes.
(11) Should it rain tomorrow, we would stay at home.
二、名词性虚拟语气：
在表示命令、建议、要求、惊叹时的名词性从句中需用虚拟语气，基本句型：
句型4：主语+(should)+动词原形
(12) Mother insisted that John (should) go to bed at 9 o’clock.(宾语从句)
(13) It was required that the crops (should) be harvested at once.(主语从句)
(14) It is surprising that she shouldn’t pass the math exam. (主语从句)
(15) The suggestion that he (should) be invited was rejected.(同位语从句)
(16) Their demand is that their wages (should) be increased.(表语从句)
注意：在这种句子中绝不可以出现would, must, could等。
三、虚拟语气在一些特殊词中的使用或含蓄条件句：
句型5：wish后的宾语从句
与现在愿望不一致：主语+过去时;
与过去愿望不一致：主语+ had +过去分词 / could + have +过去分词;
与未来愿望不一致：主语+ would / could +动词原形。如;
(17) I wish I were you.
(18) I wish I had visited the White House when I was in the States.
(19) I wish I could meet you tomorrow at the party.
句型6：It’s time句型(当It’s time后用that从句时应该为“主语+ should +动词原形”或“主语+过去时”)
(20) It’s time that you went / should go to school.
句型7：If only引起的感叹句相当于“How I wish +宾语从句”
(21) If only he could come! 他要能来就好了。
(22) If only I had known the answer! 我要早知答案就好了。
句型8：would rather, as if(though)引导的句子也需使用虚拟，表示过去的情况用过去完成时，表示现在与将来的情况
用过去时。
(23) I’d rather you posted the letter right away.
(24) I’d rather you had returned the book yesterday.
(25) She loves the children as if they were hers.
(26) Alan talked about Rome as if he had been there.
句型9：without, but, but for, but that, otherwise引起的短语或句子常暗含着虚拟条件。
(27) Without you, I would never know him.
(28) But for your cooperation, we wouldn’t have done the work so well.
(29) But that she was afraid, she would have said no.
(30) I would be most glad to help you, but I’ am busy now.
(31) I should have come to the party yesterday, but I was busy.
(32) I am busy now; otherwise I would do you the favor!
句型10：If it were not for ... / If it hadn’t been for ... (要不是因为……)，其后面的主句也需使用虚拟。
(33) If it were not for his help, I wouldn’t go home now.
(34) If it hadn’t been for the determined captain, all the passengers on the board wouldn’t have been saved.
