This chapter discusses the definitions and characteristics of the economic processes and trends in the Roman Empire, and outlines the methods by which quantification of data in written and archaeological sources can lead to a better understanding of economic integration, growth, and decline in the period c.100 BC to AD 350. These are then further analyzed in the context of a number of economic institutions and practices, including economic policy, monetization, trade, markets, commerce, investment, industrial production, technology, specialization of the labour force, and education. It suggests how we can identify a series of indicators of trends, which may be different in different regions, that can yield an idea of how the Roman economy compares with earlier and later periods of the classical world and with other cultures and empires.