‘发霉’ (fā méi) is a verb meaning ‘to become moldy’ or ‘to grow mold.’ Literally, ‘发’ (fā) means ‘to sprout,’ ‘to develop,’ or ‘to produce,’ while ‘霉’ (méi) means ‘mold’ or ‘mildew’ — the fuzzy, often greenish-black fungal growth that appears on damp, organic materials like food, wood, or fabric. Together, they describe the biological process of mold colonization under warm, humid conditions.

This word is commonly used to describe spoiled food (e.g., bread, fruit, soy sauce), damp walls, old books, or neglected stored items. It carries a negative connotation, implying spoilage, uncleanliness, or neglect. While it’s primarily literal, it can occasionally appear metaphorically in informal speech to suggest something has ‘gone stale’ or ‘deteriorated over time’ — though this usage is rare and nonstandard. The verb is intransitive and typically appears with time expressions (e.g., ‘放久了会发霉’) or passive constructions (e.g., ‘这衣服发霉了’).