because和because of的意思都是：因为，由于。
但是在用法上又有不同。
because：后加从句。
比如：She doesn't go to school because she is ill.
她没来上学因为她生病了。
在这句话中。she is ill就是从句。所以because后面就是接从句。而再来看because of。
because of：后加代词/名词/动词的ing形式。
还是拿刚才那句话来比较。用because of来代替后。就是：
She doesn't go to school because of her illness.
同样的.一个意思。接连的却不同。
her illness是名词。
这就可以说明。because of后接代词/名词/动词的ing形式。