/ waɪ; NAmE / noun , abbreviation
■ noun (also y ) ( pl. Ys , Y's , y's / waɪz; NAmE /)
1.
[ C , U ] the 25th letter of the English alphabet :
'Year' begins with (a) Y / 'Y'.
2.
[ U ] ( mathematics ) used to represent a number whose value is not mentioned :
Can the value of y be predicted from the value of x?
3.
[ U ] a person, a number, an influence, etc. that is not known or not named :
Let's suppose X knows what Y is doing.
—see also Y chromosome , Y-fronts
■ abbreviation
the Y ( NAmE , informal ) YMCA , YWCA