Inventory is listed as an asset on a firm's balance sheet and consists of the stocks or items needed to maintain production, support activities such as maintenance and repair, and provide customer service. Inventory typically is categorized based on its flow through the production cycle, using such designations as raw materials, work in process, and finished goods. Maintenance, repair, and operating supplies also are stocked to support the functionality of the firm.
For planning and forecasting purposes, inventory is classified based on the source of its demand as either independent or dependent. Independent demand items are requested directly by the customer and thus must be forecasted. Demand for dependent items can be derived or calculated based on relationships to independent items, usually noted by higher levels in the bill of material.
Reference - Inventory (APICS OMBOK Framework 5.2).