假設語態與條件句
假設語態（subjunctive mood）用來表達與事實相反的情況，做法是把動詞往過去退一格。條件句則陳述有可能發生的情況，動詞維持正常時態。分辨兩者的關鍵在於說話者認為這件事是否真實。
條件句和假設語態差在哪？
| 比較 | 條件句 | 假設語態 |
|---|---|---|
| 時間 | 有現在、過去、未來，只有談未來時 if 子句的動詞會和主要子句不同（用現在式代替未來） | 有現在、過去、未來，都用往過去退一格的動詞形式 |
| 作者的態度 | 看不出作者對事情的評論 | 作者對事情有評論，認為事情不是真的或不太可能 |
| 例句 | If it rains, we will stay home. | If I were you, I would stay home. |
假設語態有哪三種句型？
| 假設的對象 | if 子句 | 主要子句 |
|---|---|---|
| 與現在事實相反 | If + S + 過去簡單式／were／was + V-ing／were + V-ing | S + would／could／should／might + V |
| 與過去事實相反 | If + S + had + p.p. | S + would／could／should／might + have + p.p. |
| 與未來事實相反 | If + S + were to／should + V | S + would／could／should／might + V |
- 現在：If I had money, I would buy it.（現在沒錢）
- 過去：If I had studied, I would have passed.（當時沒讀書）
- 未來：If the sun were to disappear, life would end.（幾乎不可能）
在假設語態中，主詞不論單複數，正式寫作都用 were：If he were here, ...
假設語態一定要有 if 嗎？
不一定。wish、without 等句型也會用假設語態。
- I wish I were taller.
- I wish I had studied harder.
- Without your help, I would have failed.
省略 if 時，要把助動詞移到主詞前面：
- If I had known → Had I known
- If I were you → Were I you
- If you should need help → Should you need help
建議、要求類的字後面為什麼要用原形動詞？
表示建議、要求或必要的動詞和形容詞，後面的 that 子句要用 (should) + 原形動詞，should 常省略，動詞不隨主詞變化。
| 類別 | 常見的字 |
|---|---|
| 表建議 | suggest, recommend |
| 表要求 | ask, require, request, demand, insist, command, urge |
| 表必要的形容詞 | necessary, important, essential, vital, urgent, desirable |
- The doctor suggested that he (should) rest.
- It is essential that she (should) be on time.
用法補充
這些字表達「建議、要求」時才用原形動詞。如果 insist 是「堅稱」、suggest 是「暗示」，就照一般時態：He insisted that he was innocent.
練習題
1. 找出錯誤：If I was you, I will accept the offer.
這是與現在事實相反的假設，應改為 If I were you, I would accept the offer.
2. 填空：If she had left earlier, she ___ the train.（would catch／would have caught）
would have caught。if 子句是 had + p.p.，表示與過去事實相反。
3. 找出錯誤：The manager demanded that he finishes the report.
demand 表要求，that 子句用原形動詞。應改為 he (should) finish the report.
4. 省略 if 改寫：If I had known the truth, I would have told you.
Had I known the truth, I would have told you.
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if 條件句（中文）
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suggest、demand 後面的動詞
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I wish 句型
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