Wu is a variety of Chinese spoken by about 90 million people mainly in Zhejiang (浙江), Shanghai (上海), southern Jiangsu (江苏), and in parts of Anhui (安徽), Jiangxi (江西, and Fujian (福建).
Major subvarieties of Wu include those spoken in Shanghai (上海 / Zånhae), Suzhou (苏州), Ningbo (宁波), Wenzhou (温州), Hangzhou (杭州), Shaoxing (绍兴 / Zaushin), Jinhua (金华), Yongkang (永康), and Quzhou (衢州), and there are considerable differences between these subvarieties.
The Suzhou variety was traditionally the most prestigious of these, however the Shanghai variety of Wu, or Shanghainese (上海閒話), has become the most prestigious variety as a result of the size and economic dominance of Shanghai, and Wu is often referred to as Shanghainese by non-specialists. Scholars prefer to use the term Wu (吳), which comes from the name of the ancient kingdom of Wuyue (吳越) in what is now Jiangsu and northern Zhejiang provinces. This variety of Chinese is also known as Jiangnan speech (江南話), Jiangsu-Zhejiang speech or Jiangzhe speech (江浙話), or Wuyue speech (吳越語).
Wu is perceived by speakers of other varieties of Chinese as being soft, light and flowing, and as a result is sometimes called 吴侬软语 (wúnóngruǎnyǔ) or "The Tender Language of Wu"
Since the founding of the PRC in 1949, people throughout China, including in Wu-speaking areas, have been encouraged to speak Mandarin. Wu has been replaced by Mandarin in the media and schools, and many non-Wu speakers migrated to Wu areas. Nowadays people are discouraged from using Wu in public and administrative affairs, however many people ignore this.
Varieties of Wu are rarely written and few people believe it is worthwhile to write them or to develop a standard written form for them. There are a few books that teach varieties of Wu in a playful and entertaining way.
There are some TV programmes in varieties of Wu with each town having at least one if its own subvariety, however they are not allowed to broadcast during prime time.
Details of Wu varieties:
吴音小字典 (Wu dictionary)
吴语拼音 (Romanization of Wu)