Polypolies

A student asked me:

If mono means one and poly means many, what's the logic of using both terms to denote the case of a single firm in the maket (i.e., monopoly)?

After checking an etymological dictionary I realized that poly in monopoly comes from the greek root polein which means to sell. This sweet etymological logic led me to find the following -rather amusing- concept which is rarely used:

• Polypoly: when there are many sellers in a market.

Perfect competition would be a specific case of polypoly (or polipoly, there doesn't seem to be an agreement on how to spell the word).

So, it turns out that perfectly competitive markets are both polypolistic (have many sellers) and polyopsonistic (have many buyers). Also, the typical textbook case of a monopoly would more accurately be described by polyopsonistic monopoly, otherwise we could not be sure that there are many buyers in the market and the classical analysis would not work.

Anyway, this puts an end to the cultural moment of the day.