> Would you mind explaining how a company could hold monopoly power while not actually holding a monopoly?
Quite arguably, you can’t, but monopoly power (particularly, its expression as pricing power) can be observable (and itself proves an actual monopoly) when monopoly would not be clear by other means.
The ability to price without sales going to a competitor demonstrates the absence of actual competition, regardless of the superficial apparent competition in a described market.
"Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power — that is, the long term ability to raise price or exclude competitors. That is how that term is used here: a "monopolist" is a firm with significant and durable market power. Courts look at the firm's market share, but typically do not find monopoly power if the firm (or a group of firms acting in concert) has less than 50 percent of the sales of a particular product or service within a certain geographic area. Some courts have required much higher percentages. In addition, that leading position must be sustainable over time: if competitive forces or the entry of new firms could discipline the conduct of the leading firm, courts are unlikely to find that the firm has lasting market power."
Would you mind explaining how a company could hold monopoly power while not actually holding a monopoly?