by chance是介词短语，意思是“偶然;碰巧;意外地”。相当于 by accident,在句中作状语。英文解释为：
1.anything which was not meant to happen（表示任何不该发生的事，意外发生了。）
2.events that occur in the absence of an intention（在没有意图的情况下发生的事件）
By chance they both arrived at the same time. / They happened to arrive at the same time.
Our life gets better and better not by chance, but by working hard.
Silla and Racheal met by chance in a shopping mall.
She got into theater by chance.
Our meeting in hotel was by chance I swear.
I heard their secrets by chance.
I got this work by chance. I never intended to work for them.
After several years of hiding from each other, they met in Paris by chance.