英文講義--if假設語氣

If 的假設語氣

1.現在或未來可能發生的狀況(條件句)

If+ S+現在式動詞，S+ will(can,may,shall )+原形動詞

例如:If it rains tomorrow, I will not go to school.

     因為下雨，我才不用去學校。

     If he finishes his homework, his mother will let him watch

     movie or play video games.

     他要做完作業，她媽才會讓她看電影或是打電動。

     If Jane comes to my birthday party, I will be extremely excited.

     假如Jane明天來參加我的生日派對，我就會很開心。

2. 與現在事實相反                     

If+ S+過去式動詞，S+ would(could ,should, might)+原形動詞

例如:If I were rich, I would help you.

因為現在我不有錢，所以是與現在事實相反的用法

     If she got up early today, she could have a breakfast with her friends.

     因為她今天沒有早起，所以她沒跟她朋友吃早餐。

     If Jane came to my birthday party, I would be extremely excited.

     因為Jane沒有來我的生日派對，所以我不會開心。

3. 與過去事實相反

If+ S+過去完成式動詞，S+ would(could ,should, might)+have+ 過去分詞

例如:If he had told me the truth, I would not have made the mistakes.

因為他過去沒有告訴我事實，所以我犯錯了。

If I had studied hard, I would have passed the exam.

因為我過去沒有好好認真念書，所以我沒有通過考試。

If Jane had come to my birthday party, I would have been extremely excited.

因為當時Jane沒來我的生日派對，所以我當時不開心。

4. 與未來事實相反：表示對未來事情的假設，實際上絕不可能發生。

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

例如:If we were to live to 200 years old, we could change everything.

     因為我們不可能活到200歲，因此我們也不可能改變任何事。

     If university student were to hand in the homework before the end of this month, the professor would be happy. 

     因為我們不可能再月底前交作業，所以老師不會開心。

     If I were to be qualified for National Taiwan University, my mother would

     be extremely excited. 因為我不可能考上台大，所以我媽不會開心。

5. 萬一

If + S + should + 原形動詞, S + shall/will/can/may/should/would/could/might +原形動詞

à這是語意程度之別:

如果If子句所推測之事可能性微乎其微, 主觀認知會與事實相反, 就用would/should/could/might

例如: If I should have a car, I would pick you up.

      萬一我有車子的話，我就會去接妳。

      (但是事實上，我根本不會有車，我根本不會去接你。)

      If Jane should come to my birthday party, I would be extremely excited.

      萬一Jane來我的生日派對的話，我就會很開心。(但是事實上來的機會是零)

如果If子句所推測之事可能性不是微乎其微, 主觀認知有可能發生, 就用shall/will/can/may.

例如: If I should have a car, I will pick you up.

      萬一我現在有一輛車的話, 我就馬上去載你了.

      (但是事實是: 我現在雖然沒有一輛車,但是還是可能有)

      If Jane should come to my birthday party, I will

      be extremely excited.

     萬一Jane來我的生日派對的話，我就會很開心。(雖然來的機會不高，但還是

     有來的可能，只是不大)

6. if的【省略】

假設語氣的if子句中，若有:1. 過去完成式助動詞had, 2. 表示「萬一」的助動詞should，3. 用於現在假設語氣的be動詞were出現時，可以將這些詞類置於主詞前，並將if省略。

例如: If he had told me the truth, I would not have made the mistakes.

    àHad he told me the truth, I would not have made the mistakes.

      If I were rich, I would help you.

    àWere I rich, I would help you.

      If I should have a car, I would pick you up.

    àShould I have a car, I would pick you up.

6. 表【好像】的假設法

S+V as if + S + 現在式動詞  (表極大可能)

It looks as if/as though it is going to rain. （看起來好像要下雨了）

S+V as if + S + were/過去式V  (與現在事實相反)

He talks as if he were a doctor. (他的談吐好像他是個醫生)

Mr. Wang loves me as if/as though I were his own child.(事實上他根本不愛我)

S+V as if + S + had + Vp.p.  (與過去事實相反)

He talks as if he had known the news yesterday.(他說話的樣子好像他昨天以知道這個消息)

He looked as if/as though nothing had happened.(事實上他應該以前有發生什麼事)

7. 表【要求、建議】動詞+that S+ (should) 原V/ Be.+ Vp.p.

表「建議」：suggest、recommend、advise、propose、move（提議）

表「要求」：ask、desire、demand、require、request、insist

表「命令」：order、command

表「規定」：rule、regulate、stipulate

表「主張」：advocate、maintain

例如:

1. English teacher asked that I (should) recite vocabularies.

2. Doctor suggests that patients (should) take the medicine on time/ on schedule/ punctually.

8. 【lest S.+(should) + VR】 　以免／唯恐…

You must study hard lest you (should) fail the exam.

＝ You must study hard for fear that you may fail the exam.

＝ You must study hard for fear of failing the exam.

（你必須用功讀書，以免考試不及格。）

He did it carefully lest he (should) make the same mistake again.

＝ He did it carefully for fear that he might make the same mistake again.

＝ He did it carefully for fear of making the same mistake again.