a． Used to可指过去的状态或情况,would则不能.如：
School children used to know the story of how Abraham Lincoln walked five miles to return a penny he"d overcharged a customer．(不能用would)
过去,学校的孩子们都知道亚伯拉罕·林肯怎样步行5英里退还多收顾客1便士的故事.
Yet,he cannot but remember China as it used to be．然而,他不会不记得旧日的中国(不能用would).
b． Would表示反复发生的动作.如果某一动作没有反复性,就不能用 would,只能用 used to.例如：
And from that day on,as soon as the table was cleared and the dishes were gone.Mother would disappear into her sewing room to practice.
从那天起,只要碗盘撤掉、饭桌一清理干净,妈妈就马上躲进做针线活的房间练习起来.(具有反复性)
I used to live in Beijing． 我过去住在北京.(没有反复性)
c． Used to表示过去经常性或习惯性的动作或状态现在已经结束,would则表示有可能再发生.如：
People used to believe that the earth was flat．
过去,人们总以为地球是扁平的.(现在已不再这样认为)
