used to represent the second of two numbers or names that are not known or stated, when the first is represented by "x"未知(或未指明)的数(或名称)(在两个未知或未指明的数或名称中,当第一个用x代替时,y用来代替第二个)
If 2x = 3y and x = 6, then y = 4.假设2x=3y且x=6,则y=4。
The children on trial were referred to as child X and child Y.受试儿童被称作儿童X和儿童Y。