It's first and foremost an economic concept.A monopoly is a legal definition
While there's law regulating monopolies, there's - to my knowledge - no 100% clear-cut definition in law.
But they do not control the distribution of (competitors') Ford or Chevrolet cars to a quarter or half of the population.Having said that Honda has a natural monopoly on accords
Apple has a monopoly for distribution of apps to consumers on iOS. And the underlying iOS operating system itself forms a duopoly with Android in smartphone operating systems.