If引導的條件狀語從句
很多英語學習者都覺得If引導的條件狀語從句這個句型很難，學習起來很吃力。下面是學習啦小編為你整理的If引導的條件狀語從句的相關資料，希望大家喜歡!
If引導的條件狀語從句用法
1.if引導的條件狀語從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，中間要用逗號將主句和從句隔開。
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，我就來看你。
2. 在含if引導的條件狀語從句的復合句中，主句用一般將來時，從句通常用一般現在時態表示將來意義，即“主將從現”原則。
例如：
If it snows tomorrow, we will go skiing.
如果明天下雪，我們就去滑雪。
3. 在含if引導的條件狀語從句的復合句中，語句的謂語還可含有情態動詞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，我們就能出去。
4. 在含if引導的條件狀語從句的復合句中，如果主句部分描述的是客觀事實或真理，要用一般現在時。
例如：
If you heat the ice, it turns into water.
如果你加熱冰，它就會變成水。
if引導的非真實條件句
對過去的虛擬
條件從句(if):主語+had done 主句might/would/should/could+have done
對現在的虛擬
if+ 主語+動詞過去式(be用were)主句 might/would/should/could+do
對將來的虛擬
if+主語+動詞過去式(be用were)或主語+should do或主語+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.注意事項
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. 混合時間的虛擬語氣 從句為對過去的虛擬，主句是現在。
Had we not used an out-of-date timetable, we wouldn't have missed the train.
if引導從句的倒裝從句相當于 if we had not used an out-of-date timetable, 同樣，were還有should 在從句中都可以提前，省略if.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!
虛擬語氣的十大句型
一、虛擬條件句：
條件狀語從句是非真實情況，在這種情況下要用虛擬語氣。
1.條件從句與現在事實不一致，其句型為：
句型1：If +主語+過去時，主語+ should (could, would, 或might) +動詞原形
(1) If I were you, I would study hard.
(2) If it rained, I would not be here now.
2.條件從句與過去事實不一致，其句型為：
句型2：If +主語+had+過去分詞，主語+ should(could, would, 或might)+ have +過去分詞
(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.條件從句與將來事實不一致，其句型為：
句型3：If +主語+過去時/ should +動詞原形/ were to+動詞原形，主語+ should (could, would, 或might) +動詞原形
(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.
注意問題：
1.If條件句中絕對不可以出現would。
2.根據句中的時間狀語，有時可能出現“混合虛擬”的情況，即主句可能是現在的情況，條件句也許是發生在過去的情況，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.條件句中如果出現were, had, should可省去if，將主語與這些詞倒裝。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、名詞性虛擬語氣：
在表示命令、建議、要求、驚嘆時的名詞性從句中需用虛擬語氣，基本句型：
句型4：主語+(should)+動詞原形
(12) Mother insisted that John (should) go to bed at 9 o’clock.(賓語從句)
(13) It was required that the crops (should) be harvested at once.(主語從句)
(14) It is surprising that she shouldn’t pass the math exam. (主語從句)
(15) The suggestion that he (should) be invited was rejected.(同位語從句)
(16) Their demand is that their wages (should) be increased.(表語從句)
注意：在這種句子中絕不可以出現would, must, could等。
三、虛擬語氣在一些特殊詞中的使用或含蓄條件句：
句型5：wish后的賓語從句
與現在愿望不一致：主語+過去時;
與過去愿望不一致：主語+ had +過去分詞 / could + have +過去分詞;
與未來愿望不一致：主語+ would / could +動詞原形。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(當It’s time后用that從句時應該為“主語+ should +動詞原形”或“主語+過去時”)
(20) It’s time that you went / should go to school.
句型7：If only引起的感嘆句相當于“How I wish +賓語從句”
(21) If only he could come! 他要能來就好了。
(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)引導的句子也需使用虛擬，表示過去的情況用過去完成時，表示現在與將來的情況
用過去時。
(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引起的短語或句子常暗含著虛擬條件。
(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 ... (要不是因為……)，其后面的主句也需使用虛擬。
(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.