如果你想买下它，可以说 "I want to buy it." 这句话来源于英语中的主动语态，表示你主动要做某件事情。例句：

I want to buy a new car.

I want to buy some groceries.

I want to buy a ticket to the concert.

这个短语的来源源于英语中的主动语态，也就是表示你主动去做某件事情。例如：

I want to go for a walk.

I want to eat some pizza.

I want to watch a movie.

这个短语在英语中常用来表示你对某件事情有兴趣或者有意愿去做某件事情。例如：

I want to learn a new language.

I want to visit a new country.

I want to try a new sport.

总之，如果你想买下某样东西，可以说 "I want to buy it." 来表达你的意愿。