Youbian dubian (Chinese: 有邊讀邊; pinyin: yǒu biān dú biān; literally "Read the side if any"), or dubanbian (讀半邊 dú bàn biān "Read the halve"), is an (often erroneous) method 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").
Most Chinese characters consist of two parts, one of which is the semantic part (often the radical), i.e. what this character has to do with (e.g. the part 貝 (shell) indicates that a character concerns commerce, as people used shell as currency in ancient times); another of which is the phonetic part, which shows how the character is or was pronounced (see more at Chinese character classification).
The phonetic part represented the exact or almost-exact pronunciation of the character when the character was first created; and 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.