The Chinese word **霉菌 (méijūn)**, meaning "mold" or "mildew," is a compound noun formed through semantic combination. The first character, **霉 (méi)**, originally depicted something being spoiled by rain and carries the core meaning of "mildew" or "to go moldy." The second character, **菌 (jūn)**, means "fungus" or "bacterium." When combined, **霉** acts as a descriptive modifier specifying the type, resulting in the precise meaning of "mildew fungus" or "mold," a type of microorganisms that thrives in damp conditions and causes organic matter to decompose. This structure is typical of Chinese terminology, where two meaningful characters are joined to create a new, more specific concept.