A vowel diagram or vowel chart is a schematic arrangement of vowels within a phonetic system. Vowels do not differ in place, manner, or voicing in the same way that consonants do. Instead, vowels are distinguished primarily based on their height (vertical tongue position), backness (horizontal tongue position), and roundness (lip articulation). Depending on the particular language being discussed, a vowel diagram can take the form of a triangle or a quadrilateral.
The vowel diagram of the International Phonetic Alphabet is based on the cardinal vowel system, displayed in the form of a trapezium. In the diagram, convenient reference points are provided for specifying tongue position. The position of the highest point of the arch of the tongue is considered to be the point of articulation of the vowel.
