The Hindi alphabet is called Devanagari and begins with 11 vowels. Vowels are firstly taught in their independent form, that means the way they are written at the beginning of a word or following another vowel. In Hindi it is very important to stress the duration of a vowel. Vowels can be divided into simple vowels and diphthongs. Simple vowels have each one a long and short form, while diphthongs are always long. Diphthongs are pronounced in a slightly different way according to regional accent, I'll give you the standard pronunciation.