Question: when can y be used as a vowel?
Answer: When y forms a diphthong—two vowel sounds joined in one syllable to form one speech sound, such as the "oy" in toy, "ay" in day, and "ey" in monkey—it is also regarded as a vowel. Typically, y represents a consonant when it starts off a word or syllable, as in yard, lawyer, or beyond.