What is meant by a monopoly?

The legal definition of a monopoly is, any firm within an industry which possesses more than 25% market share. This can give an insight into how a 'monopoly' firm behaves, compared to firms in other forms of industries, such as a perfectly competitive or oligopolistic firm.Because of their advantage of owning the majority of the market's sales, Monopolies may risk putting prices up, as they could potentially be the only supplier within the industy, or consumers may behave irrationally and continue to buy without checking if competitors do it cheaper.Monopoly markets can be illustrated (using whiteboard) to show how they can be productively efficient, but allocatively unefficient. Though, saying that, not all monopolsistic firms are productively efficient either, as they can become lazy! N.B: Would break down and illustrate where a student would be able to get knowledge, application, analysis and evaluation marks and also how to structure new knowledge into an essay format, suitable to their according exam board.