Because, As, Since的区别

英文原文：

Hi! I'm Tim from BBC Learning English and today I'm going to tell you about three useful words: because, as and since.

These are all used to give reasons.

Because is more common than as or since and we use it when we want to focus on the reason. I'm tired because I didn't sleep very well.

When we want to give extra focus to the reason, we can put the because clause at the beginning of the sentence. Because my bed is uncomfortable, I'm getting a bad back.

As and since are more formal than because and we use them to focus on the result rather than the reason. I hope Tom's brought that comic as I wanted to borrow it from him. Noodles are popular since they're easy to cook. 

We often use as and since clauses at the beginning of the sentence. Just remember to add a comma. So, as our minute is up, I'll finish recording this video.

中文翻译：

你好！我是来自BBC Learning English的Tim，今天我要告诉你三个有用的单词：because、as和since。

这些词都用于表示原因。

Because比as或since更常用，我们使用它时想要专注于原因。我很累，因为我没睡好。

当我们想要更加关注原因时，可以将because从句放在句子开头。因为我的床不舒服，我背痛了。

As和since比because更正式，我们使用它们来强调结果而不是原因。我希望Tom带来那本漫画，因为我想从他那里借来。面条很受欢迎，因为它们容易烹饪。

我们经常在句子开头使用as和since从句。只需记得加上逗号。所以，我们的一分钟时间到了，我要结束这个视频的录制了。

测验：

1. True or false: 'Because', 'as' and 'since' are all used to give opinions

A true

B false

2.Which of these sentences is incorrect?

A Because it's a nice day, let's go outside!

B As I'm working later than usual, let's have dinner tonight.

C Since it's Saturday I don't have to work!

3.Which of these sentences focuses on the reason for something?

A I failed my exams because I didn't study.

B As she had never met him before, she didn't know what he looked like.

C Since it's quite late, shall we get a takeaway pizza?

答案：1B   2C   3A