Excerpts from lecture notes:

These notes are intended for use in courses in microeconomic theory taught at Harvard University. Consequently, much of the structure is inherited from the required text for the course, which is currently Mas-Colell, Whinston, and Green’s Microeconomic Theory (referred to as MWG in these notes). They also draw on material contained in Silberberg’s The Structure of Economics, as well as additional sources.

Economics is a social science. Social sciences are concerned with the study of human behavior. If you asked the next person you meet while walking down the street what defines the difference between economics and other social sciences, such as political science or sociology, that person would most likely say that economics studies money, interest rates, prices, profits, and the while political science considers politicians, elections, etc., and sociology studies the behavior groups of people. However, while there is certainly some truth to this statement, the things can be fairly called economics are not so much defined by a subject matter as they are united a common approach to problems. In fact, economists have written on topics spanning human behavior, from traditional studies of firm and consumer behavior, interest rates, inflation unemployment to less traditional topics such as social choice, voting, marriage, and family.