because 和because of都表示“因为”，用法有所不同。because of和because的用法详解如下：

1.because + 句子
We didn't go on holiday because we were very busy.
我们没有去度假因为我们非常忙碌。
They were very happy because their dreams came true.
他们非常开心因为他们的梦想实现了。

有关because更详细的用法，请点击查看：
because的用法

2.because of + 短语、词组
He didn't come because of the heavy rain.
因为下大雨，所以他没有来。
He was angry because of you. 
他因你而生气。


3.用because还是because of?
关键在学会区分句子和短语：
句子必须有 主语+动词 

He didn't come because of the heavy rain.
                     (名词短语，不是句子)
He didn't come because it rained heavily.
          （是句子，因为主语it后面有动词rained）

以上就是because of和because的用法。

同时须搞懂的知识：
because since as区别