the better前为什么加the,不是*前加the吗? the better和a better有什么区别?

问题描述:

the better前为什么加the,不是*前加the吗? the better和a better有什么区别?

这都要根据语境来决定:
the better (of the two) 用来表达“两个"之间比较好的一个,正如 the best 用以表达两个以上中 ”最好“ 的一个.
Of the two players, I think John is the better one.(the better of the TWO)
I think LeBron James is "the best" player In the entire NBA.

a better 的用法, 后面必须跟一个可数名词:

She is definitely a better "singer" than XXX.跟XXX比,她绝对是更好的(”一个“)歌手.