Reconstructions of Old Chinese

Although Old Chinese is known from written records beginning around 1200 BC, the logographic script provides much more indirect and partial information about the pronunciation of the language than alphabetic systems used elsewhere. Several authors have produced reconstructions of Old Chinese phonology, beginning with the Swedish sinologist Bernhard Karlgren in the 1940s and continuing to the present day. The method introduced by Karlgren is unique, comparing categories implied by ancient rhyming practice and the structure of Chinese characters with descriptions in medieval rhyme dictionaries, though more recent approaches have also incorporated other kinds of evidence.

Although the various notations appear to be very different, they correspond with each other on most points. By the 1970s, it was generally agreed that Old Chinese had fewer points of articulation than Middle Chinese, a set of voiceless sonorants, and labiovelar and labio-laryngeal initials. Since the 1990s, most authors have agreed on a six-vowel system and a re-organized system of liquids. Earlier systems proposed voiced final stops to account for contacts between stop-final syllables and other tones, but many investigators now believe that Old Chinese lacked tonal distinctions, with Middle Chinese tones derived from consonant clusters at the end of the syllable.

The major sources for the sounds of Old Chinese, covering most of the lexicon, are the sound system of Middle Chinese (7th century AD), the structure of Chinese characters, and the rhyming patterns of the Classic of Poetry (Shijing), dating from the early part of the 1st millennium BC. Several other kinds of evidence are less comprehensive, but provide valuable clues. These include Min dialects, early Chinese transcriptions of foreign names, early loans between Chinese and neighbouring languages, and families of Chinese words that appear to be related.

Middle Chinese, or more precisely Early Middle Chinese, is the phonological system of the Qieyun, a rhyme dictionary published in 601, with many revisions and expansions over the following centuries. These dictionaries set out to codify the pronunciations of characters to be used when reading the classics. They indicated pronunciation using the fanqie method, dividing a syllable into an initial consonant and the rest, called the final. In his Qièyùn kǎo (1842), the Cantonese scholar Chen Li performed a systematic analysis of a later redaction of the Qieyun, identifying its initial and final categories, though not the sounds they represented. Scholars have attempted to determine the phonetic content of the various distinctions by comparing them with rhyme tables from the Song dynasty, pronunciations in modern varieties and loans in Korean, Japanese and Vietnamese (the Sinoxenic materials), but many details regarding the finals are still disputed. According to its preface, the Qieyun did not reflect a single contemporary dialect, but incorporated distinctions made in different parts of China at the time (a diasystem).

The fact that the Qieyun system contains more distinctions than any single contemporary form of speech means that it retains additional information about the history of the language. The large number of initials and finals are unevenly distributed, suggesting hypotheses about earlier forms of Chinese. For example, it includes 37 initials, but in the early 20th century Huang Kan observed that only 19 of them occurred with a wide range of finals, implying that the others were in some sense secondary developments.

The logographic Chinese writing system does not use symbols for individual sounds as is done in an alphabetic system. However, the vast majority of characters are phono-semantic compounds, in which a word is written by combining a character for a similarly sounding word with a semantic indicator. Often characters sharing a phonetic element (forming a phonetic series) are still pronounced alike, as in the character 中 (zhōng, 'middle'), which was adapted to write the words chōng ('pour', 沖) and zhōng ('loyal', 忠). In other cases the words in a phonetic series have very different sounds both in Middle Chinese and in modern varieties. Since the sounds are assumed to have been similar at the time the characters were chosen, such relationships give clues to the lost sounds.

The first systematic study of the structure of Chinese characters was Xu Shen's Shuowen Jiezi (100 AD). The Shuowen was mostly based on the small seal script standardized in the Qin dynasty. Earlier characters from oracle bones and Zhou bronze inscriptions often reveal relationships that were obscured in later forms.

Rhyme has been a consistent feature of Chinese poetry. While much old poetry still rhymes in modern varieties of Chinese, Chinese scholars have long noted exceptions. This was attributed to lax rhyming practice of early poets until the late-Ming dynasty scholar Chen Di argued that a former consistency had been obscured by sound change. This implied that the rhyming practice of ancient poets recorded information about their pronunciation. Scholars have studied various bodies of poetry to identify classes of rhyming words at different periods.