[jp555]

Yep! Monopoly just means there's only one supplier of any commodity. It does not mean there are no alternatives.

A patent is a government-issued monopoly.

[scarface74]

In that case you can define monopoly however you want.

You could say that YCombinator has a monopoly on posts to HN.

[jp555]

The definition of a monopoly is when there is only one seller of something. That exclusivity can be achieved in a number of ways such as patents, trade secrets, or some other monopoly moat.