Answer: it is the only seller of a unique product and barriers to entry prevent other sellers from entering the market in the long run.
Step-by-step explanation:
A pure monopoly is referred to as a single supplier of a particular product in an industry. In such market, there no no substitute exists and such firms usually have a large market share.
They are price makers, profit maximizer, discriminate on prices and have a high barriers to entry. Due to their economies of scale, they prevent other sellers from entering the market in the long run.