The Devanagari script is an abugida, as written consonants have an inherent vowel, which in Standard Hindi is a schwa.
Irregular ligatures: The schwa (अ or 'ə', sometimes written 'a') implicit in each consonant of the Devanagari script is "obligatorily deleted" in Hindi at the end of words and in certain other contexts.
Schwa deletion is computationally important because it is essential to building text-to-speech software for Hindi.
[3][4] As a result of schwa syncope, the correct Hindi pronunciation of many words differs from that expected from a literal rendering of Devanagari.
It is most commonly used by young native speakers for technological applications, such as chat, emails and SMS.
ITRANS, ISCII, IAST (and the near-identical ISO 15919), and Harvard-Kyoto romanization schemes have been employed primarily for usage by non-native speakers who are more familiar with the Latin alphabet.