为什么?

Why?

I forgot to lock the door. (我忘了锁门了。)

Why? (为什么?)

为什么?

How come? *比why?还要口语。

I didn't like the movie. (我不喜欢那部电影。)

How come? (为什么?)

你怎么会那么想呢?

What makes you think that?

I think she's in love with you. (我想她爱上你了。)

What makes you think that? (你怎么会那么想呢?)

Why do you say that?

Why do you think that?

告诉我为什么。

Tell me why.

What's the reason? (理由是什么?)

是怎么发生的?

How did it happen?

My car broke down. (我的汽车出故障了。)

How did it happen? (是怎么回事?)

How did that happen?

你干吗要去做这种事呢?

What are you doing this for? *当不明白对方为什么要做毫无理由的事情的时候使用。

Why are you doing this?

What's the reason you're doing this?

Why are you doing something like this? (你干吗要干这样的事呢?)

你为什么干那样的事呢?

Why did you do that?

Why did you do that? (你为什么干那样的事呢?)

I didn't know I wasn't supposed to. (我不知道不能这样做。)

What made you do that?

Why did you do something like that?

How could you?

How could you do that?

是什么原因呢?

What causes it? *cause“成为……的原因”、“引起”。

The river is getting dirty. (那条河越来越脏。)

What causes it? (为什么会这样呢?)

What causes it? (是什么原因?)

Air pollution. (由于空气污染。)

What is it caused by?

请给我解释一下。

Explain it to me.

You'd better start explaining.

为什么不行?

Why not? *在被对方否定时，反驳对方“为什么不行?”，还含有“当然可以”、“同意”的意思。

You can't wear the red pants. (你不能穿那条红裤子。)

Why not? They're my favorite. (为什么不能?这是我最喜欢的裤子。)

Why can't I?

Is there a reason? (有理由吗?)

你怎么那么高兴?

What are you so happy about?

What are you so happy about? (你怎么那么高兴?)

It's a wonderful day. (今天是最棒的一天。)

You seem especially happy today. (你今天显得特别高兴。)

What makes you so happy? *更随意的说法。

为了什么?

What for?

I made this big box! (我做了个这么大的箱子。)

What for? (干什么用?)For what?

What is this for? (这个用来干嘛?)

为了谁?

For who?

I bought this gift today. (今天我买了一份礼物。)

For who? (给谁买的?)

Who is it for?

你旅行的目的是什么?

What's the purpose of your visit? *出境游时，边防检查官的问话。

What brought you here? (你为什么来这儿?)

没有理由不让做吧。

No reason not to.

Why do you want to do that? (你为什么想做那件事?)

No reason not to. (没有理由不让做吧。)

Why not?

What's wrong with it?

Why shouldn't I?

你怎么在这儿?

Why are you here? *根据说话方式的不同，有时会让对方听起来不礼貌。

我告诉你为什么……

I'll tell you why...

This is the reason why...

总之，是这么回事儿。

In brief, it's like this. *比较随便的说法，用在说出重点之前。虽然不是正式的说法，但可用于所有情况。

In short, it's like this.

In a word, it's like this.

To sum up, it's like this.

它的由来是这样的……

It started like this...

How did Edison make the light bulb? (爱迪生是怎样发明灯泡的呢?)

It started like this... (它的由来是这样的……)

This is its history...

This is the way it began...

原来如此!

That's why! *比较随便的说法。

Why doesn't it work? (为什么不动呢?)

You have to turn it on first. (你得先打开开关。)

Oh, that's why! (哦，是这样啊!)

所以……

That's why...

That's why I like her. (所以我喜欢她。)

I see. (我明白了。)