All vowel sounds are voiceless

In the production of a front vowel the front of the tongue is raised towards the soft palate

A back vowel is produced by raising the back of the tongue towards the soft palate

By raising the centre of the tongue to the part of the roof of the mouth which lies between the hard and the soft palate we can produce a central vowel.

Taking into account of the part of the tongue raised we can classify vowels sounds as front, back and central

With reference to the position of the tongue we can classify vowel sounds as rounded and unrounded.

The vowel sound in the English word can is a monophthong

The first and the second vowel sounds in the word serious are diphthong

/θ/ and /ð/ can occur in