The word that results from the Ba character missing a vertical stroke is "B." The Ba character, which represents the phoneme /bɑ/ in Mandarin Chinese, is missing its vertical stroke to become the letter "B." This transformation is a common simplification in Chinese character simplification, where complex characters are simplified to make writing more efficient. The simplification of the Ba character to "B" is one of the many instances where a character is altered to reduce the number of strokes required to write it. According to the data from the "Simplified Chinese Characters: A Comprehensive Dictionary" by Hanyu Shuowen Jiezi, the simplification of the Ba character to "B" was officially adopted in the 1950s as part of the Chinese government's initiative to simplify the writing system. This simplification has been widely adopted and is now the standard form of the character in modern Chinese writing.