The system for checking the quality of a product. This may be done before it is sold, and/or at earlier stages of production. Where the checking itself destroys or is liable to damage the product, quality control has to work via sampling batches of products chosen so that they are expected to have common properties, for example those processed on a given date by the same machine. The level of spending on quality control is affected both by commercial considerations of maintaining a reputation for quality, and by legal sanctions imposing penalties or awarding damages for defective products.

• decreasing balance depreciation
• decreasing function
• decreasing returns to scale
• deductibility
• deductibles
• deepening, capital
• default
• defence spending
• deferred share
• deficiency payment
• deficit
• deficit, US
• defined benefit
• defined contribution
• definite integral
• deflation
• deflationary gap
• deflator
• degrees of freedom
• deindustrialization
• Delors Report
• demand
• demand curve
• demand-deficiency unemployment
• demand-determined output