The earlier term for 'economics' was political economy. It is adapted from the French Mercantilist usage of économie politique, which extended economy from the ancient Greek term for household management to the national realm as public administration of the affairs of state.
The philosopher Adam Smith (1776) defines the subject as "an inquiry into the nature and causes of the wealth of nations," in particular as: a branch of the science of a statesman or legislator [with the twofold objective of providing] a plentiful revenue or subsistence for the people ... [and] to supply the state or commonwealth with a revenue for the publick services.
Alfred Marshall provides a still widely-cited definition in his textbook Principles of Economics (1890) that extends analysis beyond wealth and from the societal to the microeconomic level:
Economics is a study of man in the ordinary business of life. It enquires how he gets his income and how he uses it. Thus, it is on the one side, the study of wealth and on the other and more important side, a part of the study of man.
Lionel Robbins (1932) developed implications of what has been termed "[p]aerhaps the most commonly accepted current definition of the subject":
Economics is a science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.
Robbins describes the definition as not classificatory in "pick[ing] out certain kinds of behaviour" but rather analytical in "focus[ing] attention on a particular aspect of behaviour, the form imposed by the influence of scarcity.
Gary Becker, a contributor to the expansion of economics into new areas, describes the approach he favors as "combin[ing the] assumptions of maximizing behavior, stable preferences, and market equilibrium, used relentlessly and unﬂinchingly." One commentary characterizes the remark as making economics an approach rather than a subject matter but with great specificity as