Monophthongs There are twelve monophthongs. They may be classified according to the following principles 1The height of the raised part of the tongue: we distinguish open vowels, half-open vowels, half-close vowels and close vowels 2)The part of the tongue raised we distinguish front, back and central vowels 3The length of the vowel: we distinguish long vowels and short ones 4The position (or shape) of the lips: we distinguish rounded vowels and unrounded ones 5The degree of tenseness: we distinguish tense vowels and lax vowelsMonophthongs: There are twelve monophthongs . They may be classified according to the following principles: 1)The height of the raised part of the tongue: we distinguish open vowels, half-open vowels, half-close vowels and close vowels. 2)The part of the tongue raised : we distinguish front, back and central vowels. 3)The length of the vowel: we distinguish long vowels and short ones. 4)The position (or shape) of the lips: we distinguish rounded vowels and unrounded ones. 5)The degree of tenseness: we distinguish tense vowels and lax vowels