Answer: Market structures are conditioned by three main variables: number of producing companies in the market; product differentiation; barriers to entry for new companies.
In the goods and services market, the forms and markets according to these three characteristics are as follows: perfect competition, monopoly, monopolistic (or imperfect) competition, and oligopoly.
In the input market, the market forms are defined as perfect competition, imperfect competition, monopoly and oligopoly in the supply of inputs.