In summary, try to use " buy" for simple actions, and " purchase" for more formal exchanges of money for goods.

总之，请尝试在简单行为中使用buy，而在更加正式的买入交易中使用purchase。

That's an example of a " peer-to-peer transaction" or a " peer-to-peer exchange" of money and service.

这是金钱和服务的“点对点交易”或“点对点交换”的一个例子。

" Corruption" is the noun that comes from " corrupt" and often refers precisely to this exchange of money for government favors.

“corruption” 是从“corrupt” 派生出来的名词， 通常指的就是用金钱换取政府恩惠。