There are different Usages of the letter Y.
1. the twenty-fifth letter of the English alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
This letter denotes the next after X in a set of items, categories, sizes, etc. e.g. It also denotes the twenty-fifth of twenty five or more hypothetical people or things.
Y = Year. Besides, Y letter of the English Alphabet is used in Venezuela like YV as the International Vehicle Registration.
Y = Yttrium Y = Second Unknown Quantity in Mathematics usually dependent Mathematical Variable. Y = as in y-axis = vertical axis.
The most Common Noun which is used to learn this letter at the Nursery level is Yak; Y for Yak.