课代表用英语可以称作 "class representative" 或 "class rep". 这个词来自于英语中 "class" 这个单词，表示一群人或一个班级；"representative" 表示代表，"rep" 可以简写为 "representative" 的缩写。

举个例子：

John is the class representative for our English class.

Mary is the class rep for the second-year students.

The class representatives will be responsible for organizing the school trip.