Wiktionary

1. Shaanxi(ProperNoun)

   a north-central province of the People's Republic of China, and includes portions of the Loess Plateau on the middle reaches of the Yellow River as well as the Qinling Mountains across the southern part of the province.

Origin: From Mandarin 陕西. By regular Hanyu Pinyin rules, if tone marks are not written, both Shaanxi and the neighbouring province of Shanxi, to the east of Shaanxi, should be spelled "Shanxi"; the difference is in tone: Shānxī and Shǎnxī. To make the difference clear without tonal marks, the spelling "Shaanxi" was contrived (following the Gwoyeu Romatzyh romanization system developed by Yuen Ren Chao in 1925-1926) for the province of Shǎnxī, while "Shanxi" is used for the province of Shānxī. Shaanxi is the official romanization used on the Chinese Government's official Web portal. This makes "Shaanxi" the only name of Chinese provinces that has not been romanized according to pinyin rules.