Industries

Industry is the production of goods or related services within an economy. The major source of revenue of a group or company is the indicator of its relevant industry. When a large group has multiple sources of revenue generation, it is considered to be working in different industries. Manufacturing industry became a key sector of production and labour in European and North American countries during the Industrial Revolution, upsetting previous mercantile and feudal economies. This came through many successive rapid advances in technology, such as the production of steel and coal.

Following the Industrial Revolution, possibly a third of the world's economic output are derived that is from manufacturing industries. Many developed countries and many developing/semi-developed countries (People's Republic of China, India etc.) depend significantly on manufacturing industry. Industries, the countries they reside in, and the economies of those countries are interlinked in a complex web of interdependence.

Industries can be classified in a variety of ways. At the top level, industry is often classified according to the three-sector theory into sectors: primary (extractive), secondary (manufacturing), and tertiary (services). Some authors add quaternary (knowledge) or even quinary (culture and research) sectors. Over time, the fraction of a society's industry within each sector changes.

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