Monopoly Meaning:
What a firm has when it is the only seller of a good or service in a particular market. Monopolies occur because barriers to entry prevent or greatly impede other firms from entering the market and competing with the monopoly firm.

Monopoly Example:
When pharmaceutical giant Pfizer released Viagra (a very popular product) there were no other firms selling it and no substitutes for it. Hence, Pfizer had a monopoly in the market for erectile dysfunction medication.