【上期回顾】

【本期内容】

一、内容纲要

二、内容简述

（一）定义

用表示原因或理由的连词连接一个句子，充当另一个句子的原因状语，这个句子就叫做原因状语从句。

常用来连接原因状语从句的连词有：because, since, as。

（二）because

because表示“因为”，主要用来表达对方不知道的原因，是问题的直接原因，常用来回答why，这也是其他连词没有的用法。其引导的从句既可以位于主句前面，也可以位于其后面。在有前文的情况下，也可以单独存在。如：

Because it rained hard, we were late for the meeting.

We were late for the meeting, because it rained hard.

Why were you late for the meeting? Because it rained hard.

【注意】

强调原因时，只能由because引导。如：

It was because he got up late that he missed the first bus.

（三）since

since表示“既然”，往往表示双方都知道的原因，且其引导的从句往往位于主句之前。如：

Since you are here, you may as well help us with the project.

（四）as

as表示“因为”，表示双方已知的或是显而易见的原因。它的语气比because和since都更弱。如：

I left them alone, as I felt I was in the way.

As they're handmade, each one varies slightly.

（五）其他原因手段

如：

I had to do it for the simple reason that I couldn't trust anyone else.

We listened eagerly, for he brought news of our families.

She was fortunate in that she had friends to help her.