ball=to dance 跳舞
词义：n.舞会（a large formal party with dance）
have a ball (informal)狂欢；玩得痛快
Outside the boys were sitting on the ground,they were having a ball.
男孩们在户外席地而坐，他们玩得很开心。
ballet=ball（跳舞 dance）+-et（名词后缀）
词义：n.芭蕾舞（a style of dancing）
She wants to be a ballet dancer.
她想当芭蕾舞演员。
