Fanqie

[1] The introduction of Buddhism to China around the 1st century brought Indian phonetic knowledge, which may have inspired the idea of fanqie.

[2][7] When Classical Chinese poetry flowered during the Tang dynasty, the Qieyun became the authoritative source for literary pronunciations.

[8][9] During the Qing dynasty, some bilingual Chinese-Manchu dictionaries had the Manchu words phonetically transcribed with Chinese characters.

The onset (initial consonant) is represented by that of the first of the two characters (上字 "upper word", as Chinese was written vertically); the final (including the medial glide, the nuclear vowel and the coda) and the tone are represented by those of the second of the two characters (下字, "lower word").

[3]) The Qing scholar Gu Yanwu suggested that fǎn, which also meant "overthrow", was avoided after the devastating rebellions during the middle of the Tang dynasty.

However, it is possible to identify the initials and the finals underlying a large and consistent collection of fanqie by using a method that was first used by the Cantonese scholar Chen Li, in his 1842 study of the Guangyun.

[16][18] Unaware of Chen's work, the Swedish linguist Bernard Karlgren repeated the analysis to identify the initials and finals in the 1910s.

[20] The method described the pronunciations of characters in Middle Chinese, but the relationships have been obscured as the language evolved into the modern varieties over the last millennium and a half.

[21] For example, the characters of formula 東 [tuŋ] = 德 [tək] + 紅 [ɣuŋ] are pronounced dōng, dé and hóng in modern Standard Chinese; thus, the tones no longer match.

[8] In Cantonese, fanqie can be found in some dictionaries to this day, often alongside other romanization system or phonetic guides, to indicate the pronunciation of characters lacking a homophone.

For example, in the Sun Ya dictionary the character 攀 is transcribed as pinyin pān and for Cantonese pan¹ and the Cantonese tonal homophone 扳 , whereas 戀, lacking a tonal homophone, is transcribed as lyn² and 〔拉婉切〕 (l-āai + yún) to give lyún.