Monopoly is said that a market operates as a monopoly when there is a unique company that produces the entire market supply of a product and, furthermore, there are no close substitutes to the product in question. This makes the demand curve of the market that is declining, matching the demand curve for the monopolist. An example would be a monopoly only pharmacy in town. Any legal barriers:
Patents: If someone invents something it patented so that no one else can benefit from your discovery. If it was not patented anyone discover anything.
Franchise: A franchise is a contract through which ...