The word 毒瘾 is formed by directly combining two concepts: 毒, which means "poison" but is used here to signify "drugs" (particularly narcotics), and 瘾, which means "addiction" or "compulsive craving". The formation is purely ideographic and semantic, where the first character specifies the harmful substance and the second character defines the pathological condition of dependence on it, creating the complete concept of "drug addiction".