Suzhou has traditionally been the linguistic center of Wu and was likely the first place the distinct variety of Sinitic known as Wu developed. Suzhou dialect is widely considered to be the most linguistically representative of the family. It was mostly the basis of the Wu lingua franca that developed in Shanghai leading to the formation of standard Shanghainese, which as a center of economic power and possessing the largest population of Wu speakers, has attracted the most attention. Due to the influence of Shanghainese, Wu as a whole is incorrectly labelled in English as simply, "Shanghainese", when introducing the language family to non-specialists. Wu is the more accurate terminology for the greater grouping that the Shanghainese variety is part of; other less precise terms include "Jiangnan speech" (江南話), "Jiangzhe (Jiangsu–Zhejiang) speech" (江浙話), and less commonly "Wuyue speech" (吳越語).
The Wu group (Southern Wu in particular) is well-known among linguists and sinologists as being one of the most internally diverse among the Sinitic groups, with very little mutual intelligibility between varieties across subgroups. Among speakers of other Sinitic languages, Wu is often subjectively judged to be soft, light, and flowing. There is an idiom in Mandarin that specifically describes these qualities of Wu speech: 吴侬软语, which literally means "the tender speech of Wu". On the other hand, some Wu varieties like Wenzhounese have gained notoriety for their high incomprehensibility to both Wu and non-Wu speakers alike, so much so that Wenzhounese was used during the Second World War to avoid Japanese interception.
Wu dialects are typified linguistically as having preserved the voiced initials of Middle Chinese, having a majority of Middle Chinese tones undergo a register split, and preserving a checked tone typically terminating in a glottal stop, although some dialects maintain the tone without the stop and certain dialects of Southern Wu have undergone or are starting to undergo a process of devoicing. The historical relations which determine Wu classification primarily consist in two main factors: firstly, geography, both in terms of physical geography and distance south or away from Mandarin, that is, Wu varieties are part of a Wu–Mindialect continuum from southern Jiangsu to Fujian and Chaoshan. The second factor is the drawing of historical administrative boundaries, which, in addition to physical barriers, limit mobility and in the majority of cases more or less determine the boundary of a Wu dialect.
Wu Chinese, along with Min, is also of great significance to historical linguists due to their retention of many ancient features. These two languages have proven pivotal in determining the phonetic history of the Chinese languages.
More pressing concerns of the present are those of language preservation. Many[who?] within and outside of China fear that the increased usage of Mandarin may eventually altogether supplant the languages that have no written form, legal protection, or official status and are officially barred from use in public discourse. However, many analysts[who?] believe that a stable state of diglossia will endure for at least several generations if not indefinitely.
Speakers of Wu varieties are mostly unaware of this term for their speech since the term "Wu" is a relatively recent classificatory imposition on what are less clearly defined and highly heterogeneous natural forms. Saying one speaks Wu is akin to saying one speaks a Romance language. It is not a particularly defined entity like Standard Mandarin or Hochdeutsch.
Most speakers are only vaguely aware of their local variety's affinities with other similarly classified varieties and will generally only refer to their local Wu variety rather than the dialect family. They do this by affixing '話' Wo (speech) to their location's endonym. For example, 溫州話Wēnzhōuhuà is used for Wenzhounese. Affixing 閒話xiánhuà is also common and more typical of the Taihu division, as in 嘉興閒話Kashin'ghenwo for
Northern Wu (simplified Chinese: 北部吴语; traditional Chinese: 北部吳語; pinyin: Běibù Wúyǔ): Wu typically spoken in the north of Zhejiang, the city of Shanghai and parts of Jiangsu, comprising the Taihu and usually the Taizhou divisions. It by default includes the Xuanzhou division in Anhui as well, however this division is often neglected in Northern Wu discussions.
Shanghainese (simplified Chinese: 上海话/上海闲话; traditional Chinese: 上海話/上海閒話; pinyin: Shànghǎihuà/Shànghǎi xiánhuà): is also a very common name, used because Shanghai is the most well-known city in the Wu-speaking region, and most people are unfamiliar with the term Wu Chinese. The use of the term Shanghainese for referring to the family is more typically used outside of China and in simplified introductions to the areas where it is spoken or to other similar topics, for example one might encounter sentences like "They speak a kind of Shanghainese in Ningbo." The term Shanghainese is never used by serious linguists to refer to anything but the variety used in Shanghai.
Wuyue language (simplified Chinese: 吴越语; traditional Chinese: 吳越語; pinyin: Wúyuèyǔ; "the language of Wu and Yue"): an ancient name, now seldom used, referring to the language(s) spoken in the ancient states of Wu, Yue, and Wuyue or the general region where they were located and by extension the modern forms of the language(s) spoken there. It was also used as an older term for what is now simply known as Wu Chinese. Initially, some dialectologists had grouped the Wu dialects in Jiangsu under the term 吳語 Wúyǔ where the ancient Wu kingdom had been located and the Wu dialects in Zhejiang under the term 越語 Yuèyǔ where the ancient Yue kingdom had been located. These were coined however for purely historical reasons. Today, most dialectologists consider the Wu dialects in northern Zhejiang to be far more similar to those of southern Jiangsu than to those of southern Zhejiang, so this terminology is no longer appropriate from a linguistic perspective. As a result, the terms Southern and Northern Wu have become more and more common in dialectology literature to differentiate between those in Jiangsu and the northern half of Zhejiang and those in southern Zhejiang and its Wu-speaking periphery.