Although, to tell on someone sounds a little childish.

不过，" 告发某人" 这个短语有点儿幼稚的味道。

We also use the phrasal verb " to tell on" someone.

我们还使用短语动词“告诉”某人。

" To tell on someone" means to tell another person that you are doing something wrong; to tell another person that someone is doing something bad or doing something wrong.

“to tell on someone”意思是告诉另一个人你做错了什么；告诉另一个人某人正在做坏事或做错事。