Vowels are speech sounds made with no closure or constriction of the air flowing through the vocal tract. In contrast to consonants, in vowels the tongue does not touch the lips, teeth, or roof of the mouth. Different vowel sounds can be made by moving the tongue up, down, front or back within the vowel space (without touching anywhere) and rounding or spreading the lips.
Vowel sounds are often represented in a language’s orthography in an alphabetic system by the letters A, E, I, O, U and combinations of these.
While English uses these 5 letters, there are around 20 different vowel sounds in Australian English. Many languages (including Kunwinjku) only have 5 vowel sounds.