英文文法 – 假設語氣 (If, wish, as if, without)

 

If所引導的假設語氣

If所引導的假設語氣有下列幾種句型:

1. 表達跟未來事實相反:

should
  + 原形動詞,
S +
should
If +S +
were to
would
 + 原形動詞
could
might

例:1. If he should come, I would tell the truth.

2. If the sun were to rise in the west, I would marry you.

3. If photosynthesis(光合作用) were to stop, all living things would disappear.

註:If+ S+ should+原形動詞是表達“一般情況不太可能”,而If+ S+ were to+原形動詞是表達“絕對與事實真理相反”。

2. 表達跟現在事實相反:

S +
should
If +S +
were,
would
  + 原形動詞
過去式,
could
might

例:1. If I were you, I might leave at once.

2. I would buy that house if I had enough money.

3. 表達與過去事實相反:

S +
should
If +S +
had +p.p.,
would
  + have + p.p.
could
might

例:1. If you had come to the party, you might have met Jane.

2. He might have come if it had not rained.

4. 關於假設語氣應注意事項:
(a) 要利用已知動詞去判斷未知動詞,請思考下列空格的動詞結構
If+ S+ were to+原形動詞,S+____.
S+ might+ have+ p.p.+ if+ ____.

(b) 假設語氣的助動詞一律用過去式,be動詞一律用were。
(c) 假設語氣If子句可以改為倒裝結構,即(1)去掉if,(2)將should, were或had移至主詞前面。

例:1. If he should come, I would tell the truth.
= Should he come, I would tell the truth.

2. If the sun were to rise in the west, I would marry you.
= Were the sun to rise in the west, I would marry you.

3. If I were you, I might leave at once.
= Were I you, I might leave at once.

4. You might have met Jane if you had come to the party.
= You might have met Jane had you come to the party.

請務必要掌握倒裝結構,才能判斷是與未來、現在、或過去事實相反。

(d) 與過去事實相反的事若影響到現在,則主要子句動詞用would/should/could/might +原形之
結構,這種情況主要子句會有現在的時間副詞出現。

例:1. If they had built more houses ten years ago, the housing problem would not be so serious now.

 

其它假設語氣句型

除If之外,其它wish, as if, without等亦可引導假設語氣的結構。

1. wish所引導的假設語氣:

(a) 表達與未來事實相反:S+ with+ (that)+ S+ would/should/could/might+原形動詞

例:I wish I could go to the party tomorrow.

(b) 表達與現在事實相反:S+ wish+ (that)+ S+were/過去式

例:1. I wish I were a millionaire.

2. I wish I had enough money.

(c) 表達與過去事實相反:S+ wish+ (that)+ S+ had+ p.p.

例:I wish I had known he was in hospital.

註:上列結構that可以省略;此外, 假設語氣的be動詞一律用were。

2. as if (= as though, 似乎,好像):as if所引導的假設語氣結構與上述wish的結構一樣。


(a) 表達與未來事實相反:S+ V+ as if+ S+ would/should/could/might +原形

例:He looks as if he would do it.

(b) 表達與現在事實相反:S+ V+ as if+ S+ were/過去式

例:1. He looks as if he were a rich man.

2. He looks as if he liked it.

(c) 表達與過去事實相反:S+ V+ as if+ S+ had+ p.p.

例:He talked as if he had read that book.

3. with表示“若有”,without表示“若無”,亦是引導假設語氣的結構。

(a) 表達與未來或與現在事實相反:With/Without+ NP, S+ would/should/could/might +have+ p.p.

例:With your help, I might succeed now.

(b) 表達與過去事實相反:With/Without+ NP, S+would/should/ could/might +have+ p.p.

例:Without your help, I could have failed then.
註:事實上,with+ NP與without+ NP語意上等於第一節If子句的部份,故主要子句所用的動詞是一樣的。

4. 表達命令要求、堅持、建議勸告等動詞所引導的假設語氣:這類動詞常考者包括order, command, demand, ask, require(命令要求);insist, maintain(堅持);suggest, propose, recommend, advise(建議勸告)。

(a) S+ V+ (that)+ S+ (should)+原形動詞:that與should皆可省略,若省略should,則後面動詞一律用原形。

例:1. I insisted (that) he (should) come back early.

2. My sister demanded (that) he (should) apologize (道歉)。

3. Jane suggested that I (should) buy a car.

(b) It be+ p.p.+ that+ S+ (should)+原形動詞

例:1. It was required that he (should) finish his work on time.

2. It is recommended that we (should) do more exercise.

(c) It be+ adj+ that+ S+ (should)+原形:這種結構的形容詞(adj)亦是表達命令要求、堅持、建議勸告的語氣,常考的包括necessary, important, imperative, essential, insistent, advisable等。

例:1. It is necessary that he (should) make an immediate decision.

2. It is advisable that we (should) do exercise at least twice a week.

5. It+ be (about或high) +time(that)+S+過去式:表達“該是‥的時候了”。

例:1. It is time that you worked hard.

2. It is about time you went to bed.

Author: POKUYO

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