1. Definition of vowels

Vowels are sounds made with the vocal tract more open than it is for consonants. There is hardly any obstruction of the airflow.

2. Two kinds of vowels

It can be divided into simple vowels (also are called pure vowels or monophthongs ) and diphthongs with two major types of vowels.

Diphthongs falls into two categories: centering diphthongs ending in [ə] and closing diphthongs in [i] or [u].

3. Description of English vowels

The basic parameters for describing vowels are:

1) What part of the tongue is raised and how high it is raised;

Front Central  Back

2) Whether the jaw move and whether the tongue position is changed;

High  Mid  Low

3) Whether the vocal tract is constricted, i.e. whether the muscles are tense.

Tense/lax

4) Whether the lips are rounded;

Rounded/unrounded