1、because是连词，意思是：因为；由于。可用来引导让步状语从句,这时,通常用于否定句或疑问句中。还可引导表语从句。

2、because of 是复合介词，意思是：因为，由于（说明）。其后可接名词、代词、动名词或由what引导的从句（但不是直接接从句）。当主语是代词时，because of短语在句中可用作表语。

例句：

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。

He came back late because there was something wrong with his car.他回来晚了，因为汽车出了故障。

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。