Why is the monopolistic competitor's demand curve more elastic than a pure monopolist's but less elastic than a pure competitor's? What factors determine the price elasticity of demand for a monopolistic competitor?

The monopolistic competitor's demand is more elastic than the demand faced by a pure monopolist because the monopolistically competitive seller competes with many other firms producing close substitutes. The pure monopolist has no rivals at all. The price elasticity of demand faced by the monopolistically competitive firm depends on the number of rivals and the degree of product differentiation. The more rivals and the weaker the product differentiation, the greater the price elasticity of each seller's demand and the closer monopolistic competition will be to pure competition.