蓝球用英语可以称为 "blue ball" 或 "blue sphere"。这两个词的用法和中文完全一样，都是指一个蓝色的球状物。蓝球的来源源于英语中的单词 blue 和 ball。blue 指的是颜色，ball 指的是球状物。

例句：

The blue ball rolled down the hill.

Can you pass me the blue sphere?

The blue ball is one of my favorite toys.

The blue ball is made of rubber.