* Traditionally: In English, vowels are defined as sounds made with your mouth open and your tongue relatively flat. This is why "y" is often considered a consonant when it starts a word like "yes" or "yellow" because the sound is made with a more restricted mouth opening.
* Phonetically: Phonetically, vowels are sounds produced with no obstruction of airflow in the mouth. The sound of "y" in words like "yes" and "yellow" is actually quite similar to the vowel sound in words like "see" or "bee," which is why it can be considered a vowel in these cases.
* The Letter 'Y' is Versatile: The letter "y" can act as both a consonant and a vowel depending on its position and pronunciation. In some words, like "myth" or "fly," the "y" sound is more clearly a consonant.
So, the answer is that "y" can be both a consonant and a vowel depending on how it's used.