In economics, products produced together from the same production process are called joint products.
Joint products arise when one production activity generates two or more economically significant outputs. Refining crude oil produces gasoline, diesel, jet fuel, and other petroleum products. Processing cattle can produce beef, leather, and other outputs. Because these products share inputs or stages of production, changing the output of one may affect the quantities or costs of the others.
Joint products are different from complements in consumption. Complements are goods people use together, such as printers and ink cartridges, while joint products are linked on the production side. They are also different from by-products: a by-product may have lower value or be incidental, whereas joint products are generally important outputs of the same process.
Businesses often allocate common production costs across joint products for accounting purposes. However, those allocated figures do not necessarily represent the true incremental cost of producing each individual product.