假設語氣The Subjunctive Mood

核心觀念：往過去退一格，表示「不是真的」

國中學的 If it rains, we will stay home. 是「有可能發生」的條件句（直說法）。假設語氣講的是「事實不是這樣」，英文用時態往後退一格來表示這種距離感：談現在的不真實，用過去式；談過去的不真實，用過去完成式。be 動詞在正式英文裡一律用 were，不論主詞是誰。中文只要加「要是、早知道」就好，動詞不變，所以最容易忘記退時態。

• If I had more time, I would join the robotics club.要是我有更多時間，我就會參加機器人社。（事實：現在沒時間）

• If I were you, I would apologize to her.如果我是你，我會跟她道歉。

• If we had left earlier, we would have caught the train.要是我們早點出門，就趕上火車了。（事實：過去沒趕上）

三種假設句的時態

判斷法：先問「事實是什麼時候」，再把時態往後退一格。混合假設最常見的線索是主要子句有 now、today、still。

wish、if only、as if、It's time

wish 和 if only 後面接的是「不會成真」的願望，時態一樣往後退：對現在的遺憾用過去式，對過去的懊悔用 had + p.p.，對未來的抱怨或期待別人改變用 would + V。as if / as though 表示「好像……（其實不是）」，也用過去式或 had + p.p.。It's (high) time + 過去式，表示「早就該做了，卻還沒做」。

• I wish I were taller.真希望我長高一點。（現在）

• I wish I had listened to my teacher.真希望當時有聽老師的話。（過去）

• He talks as if he knew everything.他說話的樣子好像什麼都知道。

• It's time we went home.我們該回家了。

省略 if 的倒裝：Were I…, Had I…, Should you…

正式英文可以把 if 拿掉，改成助動詞放句首的倒裝：if 子句裡有 were、had、should 時才能這樣做。Had it not been for… 與 But for… / Without… 都表示「要不是有……」。注意否定倒裝要寫 Had I not known，不能縮寫成 Hadn't I known。

• Were I in your position, I would accept the offer.如果我站在你的立場，我會接受這個工作。

• Had I known about the typhoon, I would have changed my flight.要是我早知道有颱風，就會改機票了。

• Should you need any help, please contact the front desk.萬一您需要協助，請聯絡櫃台。

• Had it not been for your support, I would have given up.要不是有你的支持，我早就放棄了。

常見錯誤

• ✗If I have wings, I would fly to see you.
  ✓If I had wings, I would fly to see you.與現在事實相反，if 子句要用過去式。
• ✗If you had come to the party last night, you would meet my cousin.
  ✓If you had come to the party last night, you would have met my cousin.見面也發生在昨晚，與過去事實相反，主要子句要用 would have + p.p.。
• ✗If I would have enough money, I would buy a new phone.
  ✓If I had enough money, I would buy a new phone.would 只放在主要子句，if 子句用過去式。
• ✗I wish I can speak Japanese.
  ✓I wish I could speak Japanese.wish 表示不會成真的願望，can 要退成 could。
• ✗Hadn't I missed the bus, I would have been on time.
  ✓Had I not missed the bus, I would have been on time.省略 if 的倒裝不能用否定縮寫，要寫 Had I not + p.p.。