Question

In what sense is a natural monopoly "natural"?

Short answer

A monopoly is natural when the structure of the market makes it unreasonable to have multiple competing firms, this is the case for products that require large-scale infrastructure. Extremely high natural cost of entry.

Step-by-step solution

Step 1. Meaning of Natural Monopoly.

A natural monopoly implies that the controlling firm has engaged in zero exclusionary practices to discourage competition. The monopoly exists in a separate uncontrollable facet, such as natural limitations of land or astronomically high capital investment costs.
Examples of a natural monopoly are electricity and water, as competitors would have to establish their own country spanning system of pipes or wires.