37.8% of online retail.

Walmart is #2 at 6.3%.

https://en.wikipedia.org/wiki/Monopoly

> The verb monopolise or monopolize refers to the process by which a company gains the ability to raise prices or exclude competitors. In economics, a monopoly is a single seller. In law, a monopoly is a business entity that has significant market power, that is, the power to charge overly high prices, which is associated with a decrease in social surplus.

> Product substitutability: Product substitution is the phenomenon where customers can choose one over another. This is the main way to distinguish a monopolistic competition market from a perfect competition market.