Conditional

Conditional sentences 就是一句句子中含有 條件性質(Conditions)，而這條件，一般人只認識單純是 " 因為…所以 "，但事實上並不全是。它的範圍可以包括：
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Format

知道它們有那幾種用法後，怎麼樣運用呢？不是隨隨便便掉個 conditional word （ if…then…else ）上去就了事吧…這個當然哩！首先， Conditional sentences 可分為 四種類 ：

真理 （ General conditionals ）、
真實假設 （ Open Present or future conditionals ）、
虛設假設 （ Unreal Present or future conditionals ）、
過去虛設假設 （ Unreal Past conditionals ）。

其次，每句 Conditional sentence 都有一句 條件句 （ if-clause ） 及一句 主句 （ main-clause ）。 條件句 就是提出條件（例如： 如果 什麼什麼什麼…）， 主句 就是擺放 " will/ shall/ may… " ，說及 結果 （例如： 那就 這樣這樣這樣…）。合併一起便成為一句 Conditional sentence （ 如果 什麼什麼， 那就 這樣這樣噢。）。Get it？

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而那四種類 Conditionals 用起來有不同的意義。用法及文法的主要分辨在於它們的 Tenses ，來個逐一剖析吧：

Truth (General conditionals)

固名詩意，這是一個基於 真理 （ General truth ） 上的假設，來說及一些 不變定律 或 習慣性 的情況。
Basic form :
if-clause
present simple
main clause
present simple


e.g.： If we eat *contaminated（受污染） food, we become ill.
e.g.： If we don't feel well, we see a doctor.
e.g.： If we boil water to 100℃, it changes into steam.
第一句及第三句是 general truth 。水滾當然都蒸發哩。食錯東西當然會病囉。
而第二句則是 habit 。病了通常都會去看醫生。

* Contaminated food 是 Participle 其中一用法，詳細可到 Participle

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Real (Open Present or future conditionals)

真實的假設 ，是我們最常用的一種。就是說及 一些現在發生的事，可能會造成將來那些結果 。
Basic form :
if-clause
present tense
main clause
future tense


e.g.：If it rains tomorrow morning, we will cancel our picnic.
e.g.：If you are hungry now, I will make you some hot cakes.
e.g.：If you want to read the book, I will lend it to you.
這三句例子都十分普通，但其實 real conditionals 可以有幾種改變，發揮出不同的效果，其中有一些還較鮮為人知呢：

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Unreal
(Unreal Present or future conditionals
及
Unreal Past conditionals)

當我們想表達一些 不真實，沒可能發生的假設時 （例如：如果我是女仔，那麼…），我們 不可以 用上一般的 " if I am..., I will..."，因為這是沒可能的，我是男仔，不論任何情況，何時何地（變性也好…），我都本質地是男仔，因此就算幾年後，幾萬年後，我都不會變。所以邏輯上就不可以用 " will " 這個字，那怎麼辦？那就不能用這假設嗎？
當然不能不用喇，但又怎樣用啊？又來動動腦筋，又運用多次我們的邏輯吧：為了能使用這種假設，但又不能與正常、正規的 時態邏輯 （ tense logic ）相沖…不如索性用不正常，不正規的 Tenses 來表達它們吧！
就這樣，一種奇怪地運用 Tenses 的表達方法便誕生了── Unreal Conditionals 。


Unreal Present or future conditionals：

Basic form :
if-clause
past simple
main clause
would + infinitive


你可以看見，它的格式是 Past Tense ，難道 unreal conditionals 就只可以表達過去的事，不能說現在嗎？！…冷靜…還記得 unreal conditionals 的 Tense 是不正常，不正規嗎？知道 " unreal " 一詞的意思嗎？ 偏偏它就是表達一個 現在的虛實假設，結果將（或認為）不可能發生 的事。（簡單一言以敝之：老吹、老作…）

先看看幾句例子再說吧：

e.g.： I am busy now. If I had time , I would certainly help you.
e.g.： I don't have a car. If I had one, I would take you for a ride round the town.
e.g.： I don't think it will rain tomorrow. If it did （tomorrow）, we would stay at home and do some reading instead.

第一個例子是說 "他現在很忙"，這是 事實 ，但 "如果有時間"，只是如果，但無結果…，所以這個 conditionals 便應該是 unreal 了。
第二個例子與第一個差不多。
而第三個例子，他認為明天一定不會上雨，這 信念 現在 在他心目中形成一種 堅信 ，亦即是他心目中的 truth ，所以相比地與他信念相反的 "下雨" 便是一種 unreal 的假設了，因此從他口中說出的這句 conditional sentence 亦順理成章地變成 unreal 。當然 in general 我們知道將來下不下雨是 不能百分百 地預料得到，所以 generally 應該不用 unreal 的。

Unreal Present or future conditionals 的變化：



Unreal Past conditionals

之前我們談論過的是 現在的 虛實假設 (Present unreal)，但假設一件事不但可以是 現在 ，還可以假設 過去 曾發生的事，舉個例：

"如果昨天我們上了那艘船，我們便會牽涉入該意外。幸好我們遲到，否則我們便會牽涉入內呢！"
" 昨天 " 是 Past ，" 我們遲到 " 亦是 Past ，但 " 我們上了那艘船 "這假設 是比 " 我們遲到 "的 早 ，因為我們假設 " 我們在遲到前上船 "，所以比 Past 更早，想一想對嗎？

看過實例，知道 過去假設 的存在意義後，言歸正傳，我們該怎樣表達它呢？既然它比現在 早 ，就是代表它的 時態 (Tense) 推早一個 Tense ， Present 變 Past ，那麼… Past 就變做 Past perfect 了。
就這麼樣， past unreal 就因此誕生如下了：

Basic form :
if-clause
past perfect
main clause
would + have + ppt


先給你一個例子看看：
e.g.： The whether suddenly turned bad yesterday. If we had gone out, we would have been caught in the heavy rain.

再把之前那個例子寫作英文
e.g.： If we had taken the 7:20 ferry, we would have been involved in the accident. Fortunately we were late, and so we escaped the collision.
不難明白吧。

Unreal Past 的變化：

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Mixing Unreal Present with Unreal Past


Unreal Present 與 Unreal Past 是可以合併一起的，我們通常會放 past perfect Tense 在 If-clause ，放 would + infinitive 在 main clause ：

e.g.：She is sorry for what she has done. If she had listened to our advice, she would not feel so bad now.
釋例：" she had listened to our advice " 是 過去 的假設，" she would not feel so bad now " 是 現在 的結果。（記著 unreal Present 是 現在 ， unreal past 是 過去 ）

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Other conditional expressions :

 

Unless we hurry, we'll miss our plane. (= if we don't hurry...)

You must work hard. Otherwise you'll fail the examination.
You should work hard. Otherwise you'd fail the examination.
We got up early. Otherwise we'd have missed the first ferry to Lantau.
so/as long as
You can borrow my camera
provided/providing that
you handle it carefully.
this should be a positive statement
on condititon that

She won't tell us
even though
she knows the answer.
even if

Take this mediciine and you'll be all right tomorrow.
Hurry up or/or else you'll be late.
(Let's) suppose it rained tomorrow. What would we do?
Supposing
(Let's) suppose it had rained yesterday. What would we have done?
Supposing

Imagine you had a lot of money. What would you do with it?

Imagine you had won a lot if money. What would you do with it?

What if she told you the truth? Wouls you forgive her?

What if she had told you the truth? Would you have forgiven her?
If it were not for her, I would not go to the party tomorrow.
But for her,
If it had not been for her, I wonldn't have gone to the party last night.
But for her,


Without his help, we wouldn't have succeeded. (= if it had not been for his help...)

Were someone to try to break into the house, the alarm would be activated. (= if someone tired to break into the house...)

Do you want to read this novel? if so (= if you do), you can have it. If not (= if you do not, i will lend it to Melinda.)

 

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