Question

define vowels give description of twelve monophthongs

Answer 1

The alphabets a,e ,i,o,u (some times y also)are vowels..Vowels are voice sounds from mouth...
Monopthongs are type of vowels having single perceived sound quality..Like monopthongs,dipthongs,tripthongs also present

Answer 2

Letters which are not the consonants and produce the sound with the open configuration of a vocal tract called the vowels. There are 5 English letters of vowels that are a, e, i, o, and u.  

On the manner of articulation, the classification of the vowel sound is called the monophthongs. They are 12 in numbers. These are the pure articulation of the vowel sounds.