Wu is a major group of Sinitic languages spoken primarily in Shanghai, Zhejiang province, and parts of Jiangsu province, especially south of the Yangtze River, which makes up the cultural region of Wu. The Wu languages are at times simply called Shanghainese, especially when introduced to foreigners. The Suzhounese variety was the prestige dialect of Wu as of the 19th century, but had been replaced in status by Shanghainese by the turn of the 20th century, coinciding with a period of rapid language change in the city. The languages of Northern Wu constitute a language family and are mutually intelligible with each other, while those of Southern Wu neither form a phylogenetic language family, nor are mutually intelligible with each other.