Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In micro-economics, a production function is a function that specifies the output of a firm, an industry, or an entire economy for all combinations of inputs. A meta-production function (sometimes metaproduction function) compares the practice of the existing entities converting inputs X into output y to determine the most efficient practice production function of the existing entities, whether the most efficient feasible practice production or the most efficient actual practice production. In either case, the maximum output of a technologically-determined production process is a mathematical function of input factors of production. Put another way, given the set of all technically feasible combinations of output and inputs, only the combinations encompassing a maximum output for a specified set of inputs would constitute the production function. Alternatively, a production function can be defined as the specification of the minimum input requirements needed to produce designated quantities of output, given available technology. It is usually presumed that unique production functions can be constructed for every production technology.