The word "账本" is a compound noun formed by combining two meaningful characters: "账" (zhàng), which means "account" or "financial record," and "本" (běn), which means "book" or "notebook." It is constructed through a common Chinese word-formation method called "modification," where the first character "账" specifies the type or purpose, and the second character "本" denotes the physical object. Therefore, the term literally translates to "account book" or "ledger," referring concretely to a book used for keeping financial records.