purchase：较正式用语；多指“大型的、批量的商业采购、或房产、不动产等购置活动”.
I am willing to purchase all the paintings in this gallery In exchange for you Convincing your son not to accompany Serena.
我正打算买下你画廊里的所有画,来作为劝服你儿子,停止和瑟琳娜交往的条件.
buy：表示“购买”的最常用语言,可指买各种日用品、消费品；还可以指用金钱雇佣、行贿等较抽象的“购买”.
I bought myself a car.我为自己买了一辆汽车.
She bought favour with flattery.她以阿谀奉承博得宠幸.
A few public officials can be bought.一些公务员会被收买.
