At the festival, all performers were treated equally.

equally 是形容词 equal（平等的）加上副词后缀 -ly 构成的副词形式。equal 来自拉丁语 aequalis，表示"相等的、相同的"。equally 表示"平等地、同样地"，强调没有差别或偏袒的对待方式。