"I want to buy" 的英文是 "I want to purchase."
来源：purchase 这个词来源于中世纪拉丁语 "purchasare"，意为购买或获得。
英文例句：
I want to purchase a new car.
(我想买一辆新车。)
Can I purchase tickets for the concert onpne?
(我可以在线购买音乐会的票吗？)
She decided to purchase the painting for her collection.
(她决定购买这幅画作，加入她的收藏中。)