Competition occurs when each producer maximizes its profits by choosing its own price or quantity without consulting other firms.

Competition occurs when firms charge the same price or decide on quantities
in cooperation with each other.

Competition occurs when people/firms/countries make decisions in situations in which attaining their goals depends on their interactions with others.

Competition occurs when a firm chooses their best strategy given the strategies that all the other firms have already been chosen.

Competition occurs when the monopolist’s average revenue from sales equals to the price.