废寝忘食 is a classical four-character idiom that literally means 'to abandon sleep and forget meals.' Each character contributes to this vivid image: 废 (fèi) means 'to abandon or neglect,' 寝 (qǐn) means 'sleep' or 'bedtime,' 忘 (wàng) means 'to forget,' and 食 (shí) means 'food' or 'meals.' Together, they describe intense, single-minded dedication—so absorbed in work or study that one loses track of basic bodily needs.

This idiom is commonly used to praise diligence, especially in academic, artistic, or professional contexts. It carries a positive connotation of admirable commitment, though modern usage sometimes hints at unhealthy overwork. It functions as an adverbial phrase modifying verbs (e.g., 工作、学习、钻研), and is typically placed before the verb it modifies or at the end of a clause. It appears frequently in formal writing, speeches, and educational settings—not in casual conversation.