The word 废寝忘食 is formed by directly combining four characters: 废 (to neglect), 寝 (sleep), 忘 (to forget), and 食 (food), each representing a specific action or object. These characters are arranged in a sequence where 废 modifies 寝 and 忘 modifies 食, creating the literal meaning "to neglect sleep and forget food". This construction yields an idiom that describes a person's total absorption in an activity, with the characters' individual meanings collectively conveying the concept without metaphorical abstraction.