The letter Y is so unique in the English Alphabet because Y is the only semi-vowel, which is the only letter that's a versatile speech sound and can be both a vowel and a consonant. The rest of the letters usually can only be either one of the speech sounds and can't usually be both of them. When we talk about vowels, we say: The vowels are A, E, I, O, U, and sometimes Y. We added that phrase about the Y thing because Y can sometimes behave like a vowel, but not always. When we talk about speech sounds, we usually say this: 5 vowels, 21 consonants Since Y is a semi-vowel, if include this Y thing, we can say this: 6 vowels, 21 consonants To eliminate the consonant Y point, we can say this: 6 vowels, 20 consonants To show the overlapping point, we can say this: 5 vowels, 1 semi-vowel, 20 consonants To completely eliminate the Y semi-vowel thing, we can say this: 5 vowels, 20 consonants To show the average point with the semi-vowel Y, we can say this: 5.5 vowels, 20.5 consonants This is a discrete data, therefore it's quite unsuitable to use decimals because we can't break the numbers down into decimals by counting them. When you count something, things can come in different sizes. If it's a quantitative data, then it's more quite suitable to use decimals because we can't break the numbers down into decimals when measuring. However, this is just for showing average, so using a decimal in this discrete data is still fine. To answer the question, the letter Y is so unique in the English Alphabet because it's the only semi-vowel, which is the only letter that can be both of the speech sounds.