mildew
noun [ U ] uk/ˈmɪl.dʒuː/ us/ˈmɪl.duː/
霉;霉菌
a black, green, or whitish area caused by a fungus that grows on things such as plants, paper, cloth, or buildings, usually if the conditions are warm and wet
There are patches of mildew on the walls. 墙上出现了一块块的霉斑。