Inventory is defined as: 1. Those products that are used to feed the production line (with raw materials and work-in-process items), sustain business support activities (Maintenance, Repair, and Operating supplies), and fulfil customer demands (finished goods and spare parts). 2. Inventory demand may be classed as dependent or independent. 3. The functions of inventory are Decoupling (to make one process independent from the next); Cycling (in lot/batch sizes, to reduce set-up costs and gain process capacity); Anticipating (to stock-pile inventories in the low sales period for selling in the high sales period); Pipelining (managing Goods-in-Transit); and Buffering (helping to protect against unpredictable variations in demand or supply with safety stock)