Pronounced wu dao (entering tone) in Guangyun, and yu dao (entering tone) in Jiyun, same pronunciation as "ao". Guangya explains it as the meaning of speaking. Leipian explains it as the meaning of informing. Also used in personal names. For example, Ru yi and Yu yi, found in the "Imperial Family Table" of the History of Song (Songshi). Also, Zhengzitong explains it as the meaning of a hidden saying. It is interchangeable with the character "ao".