Schwa deletion in Indo-Aryan languages

Schwa deletion, or schwa syncope, is a phenomenon that sometimes occurs in Hindustani (Hindi-Urdu), Bengali, Marathi, Kashmiri, Punjabi, Gujarati, Maithili and several other Indo-Aryan languages with schwas that are implicit in their written scripts. Some schwas are obligatorily deleted in pronunciation even if the script suggests otherwise.

Schwa deletion is important for intelligibility and unaccented speech. It also presents a challenge to non-native speakers and speech synthesis software because the scripts, including Devanagari, do not tell when schwas should be deleted.

For example, the Sanskrit word "Rāma" (IPA: [rɑːmə], राम) is pronounced "Rām" (IPA: [rɑːm], राम्) in Hindi. The schwa (ə) sound at the end of the word is deleted in Hindi.

The schwa is not deleted in ancient languages such as Sanskrit or Pali.

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.

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