如何在英語中使用條件：零、第一、第二、第三和混合。
條件句是母語中很常見的一種用法，在英語對話中引入條件句可以真正提高你的溝通水平。總共有四個條件，您將逐漸學會使用它們，顯然從最基本的條件開始——零條件和第一個條件。要大致了解所有條件的工作原理，請查看此概述，這樣您就可以開始了解它們是什麼以及何時使用它們。
什麼是條件句？
一個條件句是基於單詞「if」。條件句通常有兩個部分——一部分以「if」開頭，描述一個可能的情況，另一部分則描述其後果。例如：
If it rains, we’ll get wet.
我們也可以將條件句的兩個部分顛倒，使得「if」的部分放在第二位，這在疑問句中特別常見。例如：
What will you do if you miss the train?
How can you finish the project if you don’t have a computer?
What happens if the students don’t pass an exam?
條件句有四種類型：
0 – 零條件
1 – 第一個條件
2 – 第二個條件
3 – 第三個條件
也可以混合第二條件和第三條件。讓我們看看每個條件，看看如何使用它們。
零條件
我們使用零條件來談論永久的真理，例如科學事實和一般習慣。結構很簡單：
以下是一些範例：
If you heat water to 100°, it boils.
If you eat a lot, you put on weight.
If it doesn’t rain for a long time, the earth gets very dry.
If we go out with friends, we normally go to a restaurant.
If I’m tired, I go to bed early.
第一個條件
我們使用第一個條件來談論現在或未來的現實情況。第一個條件的結構如下：
以下是一些範例：
If you’re free later, we can go for a walk.
If they’re hungry, I’ll make some sandwiches.
If you’re not back by 5pm, give me a ring.
If he studies hard, he’ll do well in the exam.
If we arrive late, we must get a taxi.
He’ll call if he needs help.
Take a break if you’re tired.
另一種構造第一類條件句的方法是使用「unless」，其意思是「只有在...的情況下」或「除非」。與「if」一樣，「unless」後面永遠不能跟「will」，只能接現在時。 例如：
Unless you hurry up, you won’t catch the bus.
I’ll carry on doing this work, unless my boss tells me to do something else.
We’ll stay at home unless the weather improves.
第二個條件
我們使用第二個條件來談論現在或將來不太可能或不可能的情況。結構如下：
例如：
If I had more time, I’d exercise more. (But I don’t have more time so I don’t.)
If I were rich, I’d spend all my time travelling. (But I’m not rich so I can’t.)
If she saw a snake, she’d be terrified.
If he didn’t have to work late, he could go out with his girlfriend.
What would you do if you were offered a job in Canada?
You wouldn’t have to walk everywhere if you bought a bike.
一個常用於給予建議的表達方式採用第二類條件句結構。這個表達是「If I were you, I’d...」，意思是「在你的情況下，我會這麼做」。例如：
A: I’ve got a headache.
B: If I were you, I’d take an aspirin.
A: I don’t understand this.
B: If I were you, I’d ask your teacher for help.
A: This order won’t be delivered on time.
B: If I were you, I’d phone the customer to let them know.
第三個條件
我們用第三條件式來談論不可能的情況，就像第二條件式一樣，是過去的事。我們經常使用第三條件來描述遺憾。其架構如下：
以下是一些範例：
If we had left earlier, we would have arrived on time.
If you hadn’t forgotten her birthday, she wouldn’t have been upset.
If they had booked earlier, they could have found better seats.
If I hadn’t learnt English, I wouldn’t have got this job.
What would you have studied if you hadn’t done engineering?
They wouldn’t have hired you if you hadn’t had some experience abroad.
You could have helped me if you’d stayed later.
混合條件
當我們想要對過去發生的事情做出一個對現在有影響的假設時，可以將第二條件和第三條件結合在一個句子中。在這種情況下，結構是：
以下是一些範例：
If you’d studied harder, you’d be at a higher level now.
We’d be lying on a beach now if we hadn’t missed the plane.
They’d have much more confidence if they hadn’t lost so many matches.
What would you be doing now if you hadn’t decided to study?
現在您已經了解了所有英語條件句，請開始盡可能地使用它們進行練習。按照寫出的結構模式製作一些你自己的範例。如果你練習的話，使用條件就會變得容易！