How can Monopoly Power come about?

-Barriers to Entry discourages Competition to Firms with Supernormal Profits -Advertising and Product Differentiation: Firms can be a Price Makrer if Consumers Strongly Prefer their Products over other Firms (Brand, Quality..) -Few Competition in Market - If a Few Firms dominate then there will be Monopoly Power between them. NOTE: Consumers can still not buy the Product at all. Demand Curve Logic still stays the Same