Youbian dubian (simplified Chinese: 有边读边; traditional Chinese: 有邊讀邊; pinyin: yǒu biān dú biān; literally: "read the side if any"), or dubanbian (simplified Chinese: 读半边; traditional Chinese: 讀半邊; pinyin: dú bàn biān; literally: "read the half"), is a rule of thumb people use to pronounce a Chinese character when they do not know its exact pronunciation. A longer version is youbian dubian, meibian duzhongjian (有邊讀邊，沒邊讀中間 lit. "read the side if any; read the middle part if there is no side").
Around 90% of Chinese characters are phono-semantic compounds that consist of two parts: a semantic part (often the radical) that suggests a general meaning (e.g. the part 貝 [shell] indicates that a character concerns commerce, as people used shell as currency in ancient times), and a phonetic part which shows how the character is or was pronounced.
The phonetic part represents the exact or almost-exact pronunciation of the character when the character was first created; characters sharing the same phonetic part had the same reading. Linguists rely heavily on this fact to reconstruct the sounds of ancient Chinese. However, over time, the reading of a character may be no longer the one indicated by the phonetic part due to sound change and general vagueness.
When one encounters such a two-part character and does not know its exact pronunciation, one may take one of the parts as the phonetic indicator. For example, reading 詣 (pinyin: yì) as zhǐ because its "side" 旨 is pronounced as such. Some of this kind of "folk reading" have become acceptable over time - listed in dictionaries as alternative pronunciations, or simply become the common reading. For example, people read the character 町 ting in 西門町 (Ximending) as if it were 丁 ding. It has been called a "phenomenon of analogy", and is observed in as early as the Song Dynasty.
- Cf. Qiu Xigui, Chinese Writing, trans. Gilbert L. Mattos and Jerry Norman, Early China Special Monograph Series No. 4, Berkeley: The Society for the Study of Early China and the Institute of East Asian Studies, University of California, Berkeley, 2000, §8.6.
- Zhu Jianing 竺家寧, "Songdai yuyin de leihua xianxiang" 宋代語音的類化現象, in Jindai yin lunji 近代音論集, Taipei: Taiwan xuesheng shuju, 1994, pp. 159-172.