1 [C,U] (plural Y's;y's /waɪz ||; waɪz/) the twenty-fifth letter of the English alphabet 英语字母表的第二十五个字母: ‘Yawn’ begins with (a) ‘Y’. yawn以字母Y开头。

2 [U] (mathematics数学) used to represent a number whose value is not mentioned （用于代表未知数或变量）: Can the value of y be predicted from the value of x? 从x值能否推算出y值？

3 [U] a person, a number, an influence, etc that is not known or not named 未知的人、数及影响等: Let's suppose X knows what Y is doing. 我们假设X知道Y在做什么。 ☞Look at Y chromosome. 参看Y chromosome。