Schwa deletion in Indo Aryan languages

Hindi

Although the Devanagari script is used as a standard to write Modern Hindi, the schwa ('ə') implicit in each consonant of the script is "obligatorily deleted" at the end of words and in certain other contexts, unlike in Sanskrit. That phenomenon has been termed the "schwa syncope rule" or the "schwa deletion rule" of Hindi. One formalisation of this rule has been summarised as ə → ∅ /VC_CV. In other words, when a schwa-succeeded consonant is followed by a vowel-succeeded consonant, the schwa inherent in the first consonant is deleted. However, that rules sometimes deletes a schwa that should remain and sometimes fails to delete a schwa when it should be deleted. The rule is reported to result in correct predictions on schwa deletion 89% of the time.

Schwa deletion is computationally important because it is essential to building text-to-speech software for Hindi.

As a result of schwa syncope, the Hindi pronunciation of many words differs from that expected from a literal Sanskrit-style reading of Devanagari. For instance, राम is pronounced Rām (not Rāma, as in Sanskrit), रचना is pronounced Rachnā (not Rachanā), वेद is pronounced Véd (not Véda) and नमकीन is pronounced Namkeen (not Namakeena). The name of the script itself is pronounced Devnāgrī, not Devanāgarī.

Correct schwa deletion is also critical because the same letter sequence is pronounced two different ways in Hindi depending on the context. Failure to delete the appropriate schwas can then change the meaning. For instance, the letter sequence 'रक' is pronounced differently in हरकत (har.kat, meaning movement or activity) and सरकना (sarak.na, meaning to slide). Similarly, the sequence धड़कने in दिल धड़कने लगा (the heart started beating) and in दिल की धड़कनें (beats of the heart) is identical prior to the nasalisation in the second usage. However, it is pronounced dhadak.ne in the first and dhad.kane in the second.

While native speakers pronounce the sequences differently in different contexts, non-native speakers and voice-synthesis software can make them "sound very unnatural", making it "extremely difficult for the listener" to grasp the intended meaning.

Other Indo-Aryan languages

Different Indo-Aryan languages can differ in how they apply schwa deletion. For instance, medial schwas from Sanskrit-origin words are often retained in Bengali even if they are deleted in Hindi. An example of this is रचना/রচনা which is pronounced rachana (/rətʃənaː/) in Sanskrit, rachna (/rətʃnaː/) in Hindi and rochona (/rɔtʃona/) in Bengali. While the medial schwa is deleted in Hindi (because of the ə → ∅ / VC_CV rule), it is retained in Bengali.

On the other hand, the final schwa in वेद /বেদ is deleted in both Hindi and Bengali (Sanskrit: /veːd̪ə/, Hindi: /veːd̪/, Bengali: /bed̪/).

Gujarati

Gujarati has a strong schwa deletion phenomenon, affecting both medial and final schwas. From an evolutionary perspective, the final schwas appear to have been lost prior to the medial ones.

Nepali

Its Sanskrit tradition makes schwas be rarely deleted in Nepali except for in Hindi or Urdu loanwords. Thus, conjunctions and ligatures are used more extensively than in many other Indo-Aryan languages. For example, the word लाग्छ (Lagchha) contains a ligature between ग and छ and is pronounced with the schwa at the end.

Bengali

Bengali deleted schwas at end but retained the medial schwas.

Maithili

Maithili's schwa deletion is similar to Hindustani, and ə → ∅ / VC_CV also selectively applies to the language. For instance, हमरो is həməro (even ours) with schwas but is pronounced həmro. That is akin to the neighbouring Bhojpuri in which हमरा (meaning mine) is pronounced həmrā rather than həmərā from the deletion of a medial schwa.

Kashmiri

In the Dardic subbranch of Indo-Aryan, Kashmiri similarly demonstrates schwa deletion. For instance, drāksha (द्राक्ष, drākshə) is the Sanskrit word for grape, but the final schwa is dropped in the Kashmiri version, which is dāch.

Punjabi

Punjabi has broad schwa deletion rules: several base word forms (ਕਾਗ਼ਜ਼, کاغز, kāghəz/paper) drop schwas in the plural form (ਕਾਗ਼ਜ਼ਾਂ, کاغزاں, kāghzāṅ/papers) as well as with instrumental (ਕਾਗ਼ਜ਼ੋਂ, کاغزوں, kāghzōṅ/from the paper) and locative (ਕਾਗ਼ਜ਼ੇ, کاغزے, kāghzé/on the paper) suffixes.

Marathi

In Marathi, the schwa at the end of the Sanskrit stems is retained in such cases as a few tatsama words.

Common transcription and diction issues

Since Devanagari does not provide indications of where schwas should be deleted, it is common for non-native learners/speakers of Hindi, who are otherwise familiar with Devanagari and Sanskrit, to make incorrect pronounciatins of words in Hindustani and other modern Indo-Aryan languages. Similarly, systems that automate transliteration from Devanagari to Latin script by hardcoding implicit schwas in every consonant often indicate the written form rather than the pronunciation. That becomes evident when English words are transliterated into Devanagari by Hindi-speakers and then transliterated back into English by manual or automated processes that do not account for Hindi's schwa deletion rules. For instance, the word English may be written by Hindi speakers as इंगलिश (rather than इंग्लिश्) which may be transliterated back to Ingalisha by automated systems, but schwa deletion would result in इंगलिश being correctly pronounced as Inglish by native Hindi-speakers.

Some examples are shown below:

Vowel nasalisation

With some words that contain /n/ or /m/ consonants separated from succeeding consonants by schwas, the schwa deletion process has the effect of nasalising any preceding vowels. Here are some examples in Hindustani:

sən.kī (सनकी, سنکی, whimsical) in which a deleted schwa that is pronounced in the root word sənək (सनक, سنک, whimsy) converts the first medial schwa into a nasalised vowel.

chəm.kīlā (चमकीला, چمکیلا, shiny) in which a deleted schwa that is pronounced in the root word chəmək (चमक, چمک, shine) converts the first medial schwa into a nasalised vowel.