The relationship among the Chinese spoken and written languages is complex. It is compounded by the fact that spoken variations evolved for centuries, since at least the late Hàn Dynasty, while written Chinese changed less.
Written Chinese originated some 4000 years ago in China. It employs about 5,000 commonly used characters that each represent a morpheme. Combinations of characters produce Chinese words. The writing system is considered to have been a unifying force for much of Chinese history, transcending differences in spoken language. From the time of the Qin Dynasty onwards, a standard written language (at first Classical Chinese and later Vernacular Chinese) has been in place to bridge gaps between the various forms of spoken Chinese.
Until the 20th century, most formal Chinese writing was done in Classical Chinese or Literary Chinese (文言 wényán), which was very different from any spoken variety of Chinese, much as Classical Latin differs from modern Romance languages. Since the May Fourth Movement of 1919, the formal standard for written Chinese was changed to Vernacular Chinese (白話/白话 báihuà), which, while not completely identical to the grammar and vocabulary of dialects of Mandarin, was based mostly on them. The term standard written Chinese now refers to Vernacular Chinese.
Chinese characters represent morphemes or part of a morpheme independent of phonetic change. For example, although the number "one" is yi in Mandarin, yat in Cantonese and yit in Hokkien (form of Min), they derive from a common ancient Chinese word and can be written with an identical character ("一"). Nevertheless, the orthographies of Chinese dialect groups are not completely identical, and their vocabularies have diverged. In addition, while colloquial vocabularies are often different they also share vocabulary that is derived from the Classical written language . Colloquial non-standard written Chinese usually involves "dialectal characters" which are not used in other dialects or characters that are considered archaic in standard written Chinese.
Cantonese is unique among non-Mandarin regional languages in having a written colloquial standard, used in Hong Kong and by non-Standard Mandarin speaking Cantonese speakers overseas, with a large number of unofficial characters for words particular to this variety of Chinese. By contrast, the other regional languages do not have such widely used alternative written standards. Written colloquial Cantonese has become quite popular in online chat rooms and instant messaging, although for formal written communications Cantonese speakers still normally use standard written Chinese.
Also, in Hunan, some women wrote their local language in Nü Shu, a syllabary derived from Chinese characters. The Dungan language, considered a dialect of Mandarin, is also nowadays written in Cyrillic, and was formerly written in the Arabic alphabet, although the Dungan people live outside China.
