Phonology
The Wu dialects are notable among Chinese languages in having kept the "muddy" (voiced, or more precisely slack voiced) plosives and fricatives of Middle Chinese, such as /b̥/, /d̥/, /ɡ̊/, /z̥/, /v̥/, etc., thus maintaining the three-way contrast of Middle Chinese stop consonants and affricates, /p pʰ b̥/, /tɕ tɕʰ d̥ʑ̊/, etc. (For example, 「凍 痛 洞」 /t tʰ d̥/, where other varieties have only /t tʰ/.) Because Wu dialects never lost these voiced obstruents, the tone split of Middle Chinese is still allophonic, and most dialects have three syllabic tones (though counted as eight in traditional descriptions). In Shanghai, these are reduced to two word tones.
See Suzhou dialect, Hangzhou dialect, Changzhou dialect, Shanghainese, Quzhou dialect, Jiangshan dialect and Wenzhounese for examples of Wu phonology.
Read more about this topic: Wu Chinese