What is middle letter of vowel?

The question is a bit tricky! There isn't one single "middle letter" of all the vowels. Here's why:

* Vowels are not in a linear order: Unlike the alphabet, vowels are spread out (A, E, I, O, U).

* "Middle" depends on arrangement: If you arrange them in alphabetical order (AEIOU), the middle letter is I. However, there are other ways to arrange them (like alphabetical by sound), which would give a different "middle" letter.

So, there's no definitive answer to the question!