Thursday, 18 August 2011

Conditional Sentences




Conditional sentences 可以分為兩部分:if-clausemain clause;譬如說: 


If I see Mary, I shall let you know. 

"If I see Mary" 是 if-clause,而 "I shall let you know" 就是 main clause

Conditional sentences 一般分為三種:Type 1, Type 2, 和 Type 3

我們先看看 Type 1。

Conditional sentences type 1 是最為人熟悉的。譬如說: 

If you run, I will shoot. 
If he lies, his parents will punish him.
The dog will bite you if you run.
If we catch the 5 o'clock train, we will be in time. 

我們可以看到,if-clause 中的動詞是現在式 (present tense),而 main clause 的動詞是未來式 (future simple)。

Conditional sentences type 1 暗示的是:if-clause 內提及的行動是有可能會發生的。這一點跟 conditional sentences type 2 有明顯分別。

In short, type 1 = probable.

這種句子帶出的時態,可以是現在,也可以是未來。

除了以上的基本句子結構 (if + present + future),conditional sentences type 1 還可以有其他的變異:

1) if + present + may/might/can/must/should 

If the rain gets heavier, the trip might be cancelled.
If you don't get your act together, your boss may fire you.
If it stops raining, we can go out.
If you want to get a good grade, you must work hard. 
If you want to lose weight, you should eat less.

2) if + present + another present (通常用於表達必然發生的事) 

If you heat ice, it melts. 
If there is a shortage of anything, prices of that thing go up.

3) if + present continuous 

If you are looking for Jack, you'll find him in his room.
If you are still working on your project, you had better hurry up.
If the lift is still not working, we'll have to use the stairs.

4) if + present perfect 

If you have finished with your calculator, I'd like to use it.
If you have written your letter, I'll post it for you. 

晚一點再跟大家分享 conditional sentences types 2 & 3 的結構和用法。

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