The reduction in long-run average and marginal costs arising from an increase in size of an operating unit (a factory or plant, for example). economics of scale can be internal to an organization (cost reduction due to technological and management factors) or external (cost reduction due to the effect of technology in an industry). See also diseconomies of scale. 
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USAGE EXAMPLE

Big companies are often more profitable than smaller ones because of economies of scale: suppliers may offer discounts for larger orders, shippers may decrease per trip costs to compete for a large volume of business, and necessary production management staff may increase internal manufacturing efficiency.