Do you notice anything peculiar about the pronunciations of the following two words (written in Hindi)?
A native Hindi speaker would have no trouble distinguishing between the pronunciations of these two words: namak and nam.keen respectively. But a non-native speaker may find it unusual that although the letter म is written exactly in the same way, it is rendered slightly differently in both words.
This incongruity arises from a limitation of the Devanagari script, and also from the inconsistency in the ‘schwa deletion’ rule in Hindi. (In case you are wondering, schwa is a toneless neutral vowel sound used in some languages. It’s very common in English: for example, the ‘e’ in ‘uncle’ is a schwa. Also, the second ‘o’ in ‘Oregon’ is a schwa, as pointed out by this comic.)
In Hindi language, the schwa is implicit in each consonant, and it’s almost always deleted at the end of words. For example, कर is pronounced as kar, not kara. The schwa is deleted from the second consonant र. (Notice that करन is pronounced as karan. The implicit schwa is kept intact for र here. But not for न since it is the last consonant in the word.)
We can observe the inconsistency in this ‘schwa deletion’ rule in the two words mentioned earlier. The schwa for the letter म is present in नमक but not in नमकीन. There are numerous other examples: like सपना is pronounced as sap.na not sapana, and गुजरात is guj.rat not gujarat.
Hindi literature fails as a reliable indicator of the actual pronunciation because it is written in the Devanagari script, a syllabic writing system. In a syllabic writing system, a grapheme [such as क] represents a syllable whereas in an alphabetic writing system [such as Roman], a symbol represents one sound. Compare, for example the Roman grapheme k and its Devanagari equivalent grapheme क. The Roman symbol represents only one sound whereas the Devanagari symbol represents two. The phonetic value of क is k + a, i.e., the vowel a (called schwa and symbolized phonetically as [ə]) is inherently present in the Devanagari consonant symbol. Although in actual Hindi the inherent vowel a is dropped under some conditions; the Devanagari writing system fails to mark its deletion […]
Sources: The excerpt is from A History of the Hindi Grammatical Tradition by T K Bhatia (available here).
Also, here’s an interesting white paper written by M Choudhury and A Basu that “describes the phenomenon of schwa deletion in Hindi and proposes a rule-based algorithm for solving the problem, which is required for a concatenative Text-to-Speech (TTS) system for Hindi”.
Image Courtesy: Wikipedia