假設語法

"不是所有假設語氣都是用以下規則

  若事實可能發生則用一般式！"

與事實相反之假設語法 - If

現在：

If S were/Ved, S would VR                  

【前面是過去，後面也要是過去】

If I were cold, I could cover myself with a blanket.
    如果我很冷，我可以用毯子來蓋。

If you bought this house, it would take 100 years to pay it off.
    如果你買了這間房子，你必須花一百年才能夠還清。


過去：

If S had Vpp, S would have Vpp        

【前面是過去完成，後面也要是過去完成】

Tom might not have been rescued, if he have been much farther down the street. 
如果湯姆掉到井裡更深的地方，可能就無法被救起來了。  


未來：

表不可能之事件

If S were to VR, S would VR              

  【前面是過去，後面也要是過去】

If the sun were to rise in the west, I would trust you.
如果太陽從西邊升起，我就相信你。

表萬一之事件

If S should VR, S would VR (可能性低)
If S should VR, S will VR (可能性高)
If S should VR, 祈使句


If an earthquake should hit, everyone living in the building would be in danger.
萬一發生了地震，每個住在這棟建築的人都會有危險。

If Henry should die, then his spouse and children will get all of his possessions.
萬一亨利過世了，那麼他的配偶和他的孩子就會獲得所有他的財產。

If the box should be opened, use this tape to close it.  
萬一這箱子打開了的話，就用這捆膠帶來密封它。

＊補充說明 - 與過去之事實相反

雖然是說前面用過去完成 had Vpp，後面就是過去完成 had Vpp，但由於主要子句會有一個助動詞，以致於變回了原型 have Vpp。

＊補充說明 - 與未來表不可能之事實相反

其實它原本是這樣，舉個例子：
He is to watch movie. = He is (about) to watch movie
他即將要去看電影。

和與現在事實相反的改法一樣，beV一律改成were，就變成了
He were to watch movie. 


等同 If 當假設 的字還有 ：

Suppose、Suppoing、Provided、Providing、On the condition that

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與事實相反之假設語法 - I wish

稱之為「但願」，而句型的文法觀念和上面講的 if 假設也是完全一樣的

現在、未來：

【改成過去】

I wish I could VR

   I wish I could buy this house.
   但願我能買這間房子。


過去：

【改成過去完成】

I wish I had Vpp

   I wish then I had bought this house.
    但願我那時有買這間房子。

等同 I wish 當但願 的字還有 ：


If only、Would that、Would to Heaven、Would to God、Oh that

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If子句之倒裝 - 要不是

If去掉，be動詞, 助動詞 一律丟到句首，其餘保留不動。

現在：

    If it were not for the sun and rain, plants would die.
→Were it not for the sun and rain, plants would die.

常見變化：   

   Were it not for the sun and rain, plants would die.
= But for the sun and rain, plants would die.
= Without the sun and rain, plants would die.
    要不是有陽光和雨水，植物就會死掉。


過去：

    If it had not been for the rain, the forest fire would have spread to the town.
→Had it not been for the rain, the forest fire would have spread to the town.

  常見變化：
  
  Had it not been for the rain, the forest fire would have spread to the town.
=But for the rain, the forest fire would have spread to the town.
=Without the rain, the forest fire would have spread to the town.
   要不是當時的那場雨，森林大火就會蔓延到城鎮上。