Xu Collection, Middle Volume. Radical: Rain (yǔ). Kangxi Strokes: 19. Page 1377, Entry 36. Broad Rhymes (Guangyun) and Collected Rhymes (Yunhui): Pronounced wu (falling tone). Erya (Erya), Explanation of Heaven (Shitian): When terrestrial vapors rise and the heavens do not respond, it is called fog (wu). Fog is also known as darkness (hui). Commentary: It means dim and dark. Explanation of Names (Shiming): Fog (wu) means to cover (mao); it is vapors that confuse, obstruct, and cover things. Broad Rhymes (Guangyun): The Essence of Fate (Yuanmingbao) says: When yin and yang are in chaos, fog is produced. Book of Rites (Liji), Monthly Ordinances (Yueling): Vapors and fogs are dark and obscure. Jade Chapters (Yupian): Originally written as a variant form. Broad Rhymes (Guangyun): Same as a variant form. Collected Rhymes (Jiyun): Same as a variant form. Also, Collected Rhymes (Jiyun): Pronounced meng. Also pronounced meng. Also pronounced meng. The meaning is the same.