think of;think about;think over

think of;think about;think over  
think of多用来指“想起，认为”。  这三个词组都与“想”有关，但所表达的含义有所不同。 

如：Last night，before I went to bed，I thought of my parents．昨晚我睡觉前，想起了我的父母。

What do you think of that book？你认为那本书怎么样？

  think about 多用来指“考虑某事情或对某事进行思考”。

如：Think about what you have done！想想你所做的这一切吧！

  think over意思是“仔细考虑，认真思考”。

如：Before you answer this question，please think it over．在回答这个问题之前，请认真考虑一下。