I assume that you are thinking of a pure monopoly - a single supplier. When we are talking about monopolies in this context, we mean monopoly power, monopsony

I assume that you are thinking of a pure monopoly - a single supplier. When we are talking about monopolies in this context, we mean monopoly power, monopsony etc. For example, when a firm’s ability to charge a price higher than its marginal cost with very little change in demand of their product, it has monopoly power. When deciding if a company is a monopoly, the first thing to do is 'market definition' - defining the relevant market. Is the whole mobile phone market? Can companies realistically compete if they produce only Android apps? It is in any way practical to assume that people carry two phones? Obliviously not.