an industry in that part of the economy that creates services rather than tangible objects. Economists divide all economic activity into two broad categories, goods and services. Goods-producing industries are agriculture, mining, manufacturing, and construction; each of them creates some kind of tangible object. Service industries include everything else: banking, communications, wholesale and retail trade, all professional services such as engineering, computer software development, and medicine, nonprofit economic activity, all consumer services, and all government services, including defense and administration of justice. A services-dominated economy is characteristic of developed countries. In less-developed countries most people are employed in primary activities such as agriculture and mining.

The proportion of the world economy devoted to services grew steadily during the 20th century. In the United States, for example, the service sector accounted for more than half the gross domestic product (GDP) in 1929, two-thirds in 1978, and more than three-quarters in 1993. In the early 21st century, service industries accounted for more than three-fifths of the global GDP and employed more than one-third of the labour force worldwide.

The simplest explanation for the growth of service industries is that goods production has become increasingly mechanized. Because machines allow a smaller workforce to produce more tangible goods, the service functions of distribution, management, finance, and sales become relatively more important. Growth in the service sector also results from a large increase in government employment.