This document discusses the theory of production and the law of variable proportions. It provides definitions and explanations of key concepts:
1) The theory of production examines how producers combine inputs to produce output given technological constraints. It focuses on production functions and laws of production.
2) The law of variable proportions states that as one variable input is increased while others stay fixed, marginal product will initially rise but eventually decline, leading to three stages: increasing, diminishing, and negative returns.
3) Economies of scale refer to cost advantages from increased scale of production, including internal economies from specialization and external economies from infrastructure. Diseconomies arise as firms grow beyond optimal size due to coordination problems.