Chinese characters are romanized using the Pinyin system. Chinese digraphia involves the use of both Chinese characters and Hanyu Pinyin romanization. The name Tudou is Chinese Pinyin (Romanized Chinese) for Potato. In Hanyu Pinyin, represents the voiceless retroflex affricate . Names are presented in alphabetical order using pinyin romanization. Rank names are shown below using Hanyu Pinyin and traditional Chinese characters. Chinese characters along with Hanyu Pinyin have since replaced Xiao'erjing. Transition to Hanyu Pinyin in official use is also necessarily gradual. The rules of "Hanyu Pinyin", however, specify no such practice. Nearly every intersection in the downtown area has signs in Hanyu Pinyin. Also added were Vietnamese and Chinese Pinyin letters. Their names in Mandarin pinyin are sorted in alphabetical order. The system uses romanizations derived from Tongyong Pinyin. See the pinyin table article for a summary of possible pinyin syllables (not including tones). In standard pinyin and bopomofo, however, they are represented as a separate sequence.