区别就是两者意思上都可表示每个，具体的不同如下
each用于两者或三者以上，中文意思是det. 每，各，每一，pron. 每个，各个，adj. 每个的，各自的，adv. 给每个，对各个
We drank a whole bottle each.
either one用于两者，中文意思是两者中的任何一者
The worker was bound to the master by a mutual contract that either one could repudiate， and the relationship was conceptualized as one of partnership.
