think about
think about含有思考、研究的意思，這里指對(duì)他人說過的話進(jìn)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(fù)。
think of
在有關(guān)心、為...著想的意思，經(jīng)常關(guān)心他人。表示打算、想出、關(guān)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(jié)婚嗎？
Lei Feng was always thinking of others．雷鋒總是為別人著想。
think over
意為“仔細(xì)考慮”。Think over，and you'll find a way．仔細(xì)考慮一下，你就會(huì)有辦法的。
We need several days to think this matter over．我們需要幾天的時(shí)間把這件事情仔細(xì)考慮一下。