Open your mouth and say “aaaaa.” There! You’ve just said a vowel. A vowel is a letter that represents an open sound. There are six vowels in the English language: a, e, i, o, u and sometimes y.
Y is sometimes a vowel, as in the word story although it also sometimes acts as a consonant, as in the word yes. The vocal sounds represented by vowels are open and without friction. The word vowel comes from the Old French voieul, which is based on the Latin phrase littera vocalis, or "vocal letter," from the root word vox, or "voice."