In the history of economic thought, a school of economic thought is a group of economic thinkers who share or shared a mutual perspective on the way economies function. While economists do not always fit within particular schools, particularly in the modern era, classifying economists into schools of thought is common. Economic thought may be roughly divided into three phases: premodern (Greco-Roman, Indian, Persian, Islamic, and Imperial Chinese), early modern (mercantilist, physiocrats) and modern (beginning with Adam Smith and classical economics in the late 18th century, and Karl Marx and Friedrich Engels' Marxian economics in the mid 19th century). Systematic economic theory has been developed primarily since the beginning of what is termed the modern era.
Currently, the great majority of economists follow an approach referred to as mainstream economics (sometimes called 'orthodox economics'). Economists generally specialize into either macroeconomics, broadly on the general scope of the economy as a whole, or microeconomics, on specific markets or actors.
