Vowel
A speech sound (as \ə\, \ā\, or \ȯ\) produced without obstruction in the mouth. 2 : a letter (as a, e, i, o, u) representing a vowel.
a speech sound which is produced by comparatively open configuration of the vocal tract, with vibration of the vocal cords but without audible friction, and which is a unit of the sound system of a language that forms the nucleus of a syllable.
A vowel is a sound that is made by allowing breath to flow out of the mouth, without closing any part of the mouth or throat.
Why is it called a vowel?