ABSTRACT
In general terms, vowels are voiced sounds in which the mouth is relatively open, allowing air to flow out freely. Sometimes the mouth is wide open, as in [a], sometimes less open as in [e] or [i]. The lips, too, have a part to play: in the [u] of [mun] (moon) the lips make a rounded opening to the mouth. If you consciously prevent them from doing this, the [u] simply won't come out right (try it and see). So different positions of the tongue, jaw and lips give recognizably different vowel sounds (different vowEL QUALITIES).
