1. Few sellers: There are only a few firms that dominate the market and control the majority of the market share.
2. Interdependence: The firms in an oligopoly are highly interdependent and must take into account the decisions of their competitors when making their own decisions.
3. Barriers to entry: There are significant barriers to entry that make it difficult for new firms to enter the market.
4. Non-price competition: Firms in an oligopoly often engage in non-price competition, such as advertising and product differentiation, in order to gain an edge over their competitors.