Students explore the definition of a function by playing an interactive game called "Club Function." The goal of the game is to be in the club! With students each assigned to be either a zebra or a rhinoceros, they group themselves according to the "rules" of the club function. After two minutes, students freeze in their groups, and if they are not correctly following the rules of the club function, then they are not allowed into the "club." Through this activity students come to understand that one x-coordinate can only have one corresponding y-coordinate while y-coordinates can have many x-coordinates that correspond to it.