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Hindustani (standardized Hindi and standardized Urdu) has been written in several different scripts. Most Hindi texts are written in the Devanagari script, which is derived from the Brāhmī script of Ancient India. Most Urdu texts are written in the Urdu alphabet, which comes from the Persian alphabet. Hindustani has been written in both scripts. In recent years the Latin script has been used in these languages for technological or internationalization reasons.
The Devanagari script is an abugida, as written consonants have an inherent vowel, which in Standard Hindi is a schwa. In certain contexts, such as at the end of words, there is no vowel, a phenomenon called the schwa syncope. Other vowels are written with a diacritic on the consonant letter. Devanagari is written from left to right, with a top-bar connecting the letters together.
- क्ष (क and ष) kṣ is pronounced /kʃ/ (wiktionary:क्ष)
- ज्ञ (ज and ञ) jñ is pronounced /ɡj/ (wiktionary:ज्ञ)
The schwa (अ or 'ə', sometimes written 'a') implicit in each consonant of the Devanagri script is "obligatorily deleted" in Hindi at the end of words and in certain other contexts. This phenomenon has been termed the "schwa syncope rule" or the "schwa deletion rule" of Hindi. One formalization of this rule has been summarized as ə -> ø | VC_CV. In other words, when a vowel-preceded consonant is followed by a vowel-succeeded consonant, the schwa inherent in the first consonant is deleted. However, this formalization is inexact and incomplete (i.e. sometimes deletes a schwa when it shouldn't or, at other times, fails to delete it when it should), and can yield errors. Schwa deletion is computationally important because it is essential to building text-to-speech software for Hindi.
As a result of schwa syncope, the correct Hindi pronunciation of many words differs from that expected from a literal rendering of Devanagari. For instance, राम is Rām (incorrect: Rāma), रचना is Rachnā (incorrect: Rachanā), वेद is Véd (incorrect: Véda) and नमकीन is Namkeen (incorrect Namakeena).
The Urdu alphabet is based on the Persian, which is an Arabic alphabet. Urdu is written from right to left, and most letters link together. This leads to variations in the form of a letter depending on its position in a word. Most vowels are omitted in generic texts, although they may be written for disambiguation or for pedagogical purposes. Urdu is primarily written in a calligraphic style of the script called Nasta'liq.
|Letter||Nasta‘liq||Name of letter||Transcription||IPA|
|و||و||vā'o||v, o, or ū||/ʋ/, /oː/, /ɔ/ or /uː/|
|ہ, ﮩ, ﮨ||ہ||choṭī he||h||/h/|
|ھ||ھ||do chashmī he||h||/ʰ/|
|ی||ی||ye||y, i||/j/ or /iː/|
|ے||ے||bari ye||ai or e||/ɛː/, or /eː/|
The Latin Alphabet
The Latin alphabet has been used to write Hindustani for technological or internationalization reasons. Roman Hindi and Roman Urdu uses the basic Latin alphabet. 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.
Transliteration between the three scripts can be complicated, particularly when transliterating between Devanagari and Persian scripts. One obstacle to this is that multiple different letters in one script often all correspond to the same letter in the other script. So, simple substitution often does not produce the correct spellings.
Urdu letters with similar sounds
- 4 letters ز ذ ض ظ are all ≈ Z 
- 3 letters س ص ث are all ≈ S 
- 2 letters ت ط are both ≈ T  (a third letter ٹ is also often shown as English T, but is different to the other two Urdu letters, see #retroflex consonants below.)
- 2 letters ہ ح are both ≈ H  but are sometimes regarded as distinct.
Three braille alphabets are used: Hindi and Urdu braille in India, based on Bharati braille conventions, and Urdu Braille in Pakistan, based on Persian Braille conventions. Hindi Braille is an alphabet with a not written in some environments, while for Urdu Braille in Pakistan, it seems that vowels may be optional as they are in print.
- Uddin and Begum Hindustani Romanisation
- Hindustani etymology
- Hindustani phonology
- Hindustani grammar
- Tej K. Bhatia (1987), A history of the Hindi grammatical tradition: Hindi-Hindustani grammar, grammarians, history and problems, BRILL, ISBN 90-04-07924-6,
... Hindi literature fails as a reliable indicator of the actual pronunciation because it is written in the Devanagari script ... the schwa syncope rule which operates in Hindi ...
- Larry M. Hyman; Victoria Fromkin; Charles N. Li (1988 (Volume 1988, Part 2)), Language, speech, and mind, Taylor & Francis, ISBN 0-415-00311-3,
... The implicit /a/ is not read when the symbol appears in word-final position or in certain other contexts where it is obligatorily deleted (via the so-called schwa-deletion rule which plays a crucial role in Hindi word phonology ...Check date values in:
- Monojit Choudhury; Anupam Basu; Sudeshna Sarkar (July 2004), "A Diachronic Approach for Schwa Deletion in Indo Aryan Languages" (PDF), Proceedings of the Workshop of the ACL Special Interest Group on Computational Phonology (SIGPHON), Association for Computations Linguistics,
... schwa deletion is an important issue for grapheme-to-phoneme conversion of IAL, which in turn is required for a good Text-to-Speech synthesizer ...
- Naim R. Tyson; Ila Nagar (2009 (12:15–25)), "Prosodic rules for schwa-deletion in hindi text-to-speech synthesis", International Journal of Speech Technology, 12: 15–25, doi:10.1007/s10772-009-9040-x,
... Without the appropriate deletion of schwas, any speech output would sound unnatural. Since the orthographical representation of Devanagari gives little indication of deletion sites, modern TTS systems for Hindi implemented schwa deletion rules based on the segmental context where schwa appears ...Check date values in:
- "Urdu Phonetic Inventory" (PDF). www.cle.org.pk. Center for Language Engineering. Retrieved 19 May 2020.
- Jawaid, Bushra; Ahmed, Tafseer (2009). "Hindi to Urdu Conversion: Beyond Simple Transliteration" (PDF). Proceedings of the Conference on Language & Technology 2009. Retrieved 19 May 2020.
- Bhatia, Tej K.; Khoul, Ashok; Koul, Ashok (27 August 2015). "Colloquial Urdu: The Complete Course for Beginners". Routledge. Retrieved 19 May 2020.