在一个经常使用的约定中，任何以下划线开始命名的类都表示没有相应标记的结构。

In one convention that's often used, any class that's named with an initial underscore represents a structure that does not have a corresponding tag.

youdao

所以就没有必要再用下划线表示单词起始了。

Thus there is no need to do so with an underscore character.

youdao