The prefix "oli" means "few" in Greek --- that should help you remember the characteristics of the oligopolistic market structure. There are some topics that haven't appeared here yet, but only because I'm still working on them.
Characteristics of Oligopoly
1. "Few" firms
2. "High" concentration ratio
3. Similar or different products
4. Medium to high barriers to entry
5. Mutual interdependence
More to follow.
