Few sellers ( firms in the industry), each having a considerable share of the market.

Lack of uniformity in the size of firms.  Some firms are large while others are small but all competing in the market.

The firms are interdependent, implying that the actions of one firm affect the output and pricing decisions of other firms.  E.g. a firm  can reduce the price when other firms reduce.

Massive advertisement , normally persuasive in nature, is common under oligopoly. Each firm advertises so as to maintain its share of the market.

Oligopoly is also characterized by non-price competition. Firms constantly compete with each other through improvement in the quality of their services, advertising etc but not, using price cuts and rises as a tool of competition.

The exact behavior pattern of the producer is complex and not certain. Therefore, the demand curve for the product cannot be drawn accurately under oligopoly.

Firms are price makers and not price takers because each controls a sufficient share of the market.

The degree of entry into the industry is limited by the existence of substantial barriers

Prices under oligopoly tend to be rigid because of the high level of uncertainty existing in the industry.

Because entry in the industry is blocked, firms under oligopoly enjoy abnormal profits in the longrun.