Duopoly Definition and Explanation
Duopoly definition comes from its prefix, "du" - meaning two, so -
it is a situation where two companies control a particular sector of the economy.
Furthermore, to understand duopoly definition, just remember the concept of monopoly, it is when an economic sector is controlled by one company. Their only difference is that "mono" means one.
When an economic sector is controlled by a monopoly or a duopoly, usually free competition cannot occur in that sector, since the entities controlling the sector regulate the quantities and the prices to their own benefits.