think about
think about含有思考、研究的意思，這里指對他人說過的話進行思考。表示經(jīng)常思考、研究的意思，一般不和think of換用。
I'll think about your suggestion，and give you an answer tomorrow．我要考慮一下你的建議，明天給你答復。
think of
在有關心、為...著想的意思，經(jīng)常關心他人。表示打算、想出、關心等意義，一般不與think about互換。
Helen，are you thinking of marrying Tom？海倫，你打算和湯姆結婚嗎？
Lei Feng was always thinking of others．雷鋒總是為別人著想。
think over
意為“仔細考慮”。Think over，and you'll find a way．仔細考慮一下，你就會有辦法的。
We need several days to think this matter over．我們需要幾天的時間把這件事情仔細考慮一下。