"Monopoly: the exclusive possession or control of the supply of or trade in a commodity or service."

Given that there are things such as Walmart.com, eBay, Shopify, and many hundreds of other online commerce stores, they are self-evidently not a monopoly. In fact, they don't even have a majority share of eCommerce in the US.

And they also don't have majority share in cloud services.

Nor do they have a monopoly in eBooks.

I did not say they don't have monopoly power, I said, they are not a monopoly.

(Other than obvious things such as "Amazon products"..., in which case every manufacturer or retailer is a monopoly in their own products.)

> Other than obvious things such as "Amazon products"..., in which case every manufacturer or retailer is a monopoly in their own products.

The way this argument is normally presented is somewhat intentionally obtuse. Obviously Nike has a monopoly on Nike shoes, but "Nike shoes" isn't any kind of sensible market definition because you go to a shoe store and there are a dozen brands of shoes that are all pretty fungible with each other.

But then you get into something like "GM-compatible brake pads" and that is a sensible market definition, because if you have a GM car and you need new brake pads, they need to be compatible with your car. But you'll also notice that this isn't even the same thing as GM-brand brake pads. You could get GM-compatible brake pads from a variety of OEMs that are all compatible with your GM vehicle.

Or, it could be the case that only GM makes GM-compatible brake pads. In which case they would have a monopoly in that market. Not because it's a monopoly on their brand of brake pads, but because it's a monopoly on any brand of brake pads compatible with their brand of cars -- which is something else entirely.

> Or, it could be the case that only GM makes GM-compatible brake pads. In which case they would have a monopoly in that market. Not because it’s a monopoly on their brand of brake pads, but because it’s a monopoly on any brand of brake pads compatible with that brand of cars – which is something else entirely.

> Notice that they don’t even have to be the same company.

As a specific example (and note, that you also don’t have to be the literal sole supplier to have a legal monopoly under US antitrust law), the market Microsoft was found to have monopolized in their big antitrust case was the market for operating systems for IBM-compatible personal computers.

> “Monopoly: the exclusive possession or control of the supply of or trade in a commodity or service.”

That is not the applicable definition for US antitrust law.

https://www.ftc.gov/advice-guidance/competition-guidance/gui...