Vowels are the backbone of any language for without them there can be no speech as we know it. A vowel, as opposed to a consonant, is a speech sound produced without stopping or obstructing the flow of air from the lungs. A second, familiar definition is any letter of the alphabet representing (or usually representing) the sound of a vowel. In English, as we learned in grade school, these letters are A, E, I, O, U and sometimes W and Y.
Kansil, Prince Djoli
"All-Vowel Hawaiian Words,"
Word Ways: Vol. 7
, Article 12.
Available at: http://digitalcommons.butler.edu/wordways/vol7/iss2/12