Although the Devanagari script is used as a standard to write Modern Hindi, the schwa (, sometimes written as ) implicit in each consonant of the script is "obligatorily deleted" at the end of words and in certain other contexts. The phenomenon has been termed the "schwa deletion rule" of Hindi. One formalization of the rule has been summarized as "ə → ∅ /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, the formalization is inexact and incomplete (it sometimes deletes a schwa that exists, and it fails to delete some schwas that it should) and so can yield errors. Schwa deletion is computationally important because it is essential to building text-to-speech software for Hindi.