Economic Definition of by-product. Defined.
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Term by-product Definition: One of two goods that are produced jointly using the same resource--that is, the production of one good automatically triggers the production of the other. Also termed joint products or complements-in-production, the phrase by-product is often used when one of the products is unwanted or of secondary importance. For example, sawdust is generally considered a by-product from producing lumber from trees.