1.the branch of social science that deals with the production and distribution and consumption of goods and services and their management （Princeton）

2.The study of choice and decision-making in a world with limited resources.(UIUC)

3.Social science dealing with the production, distribution, and consumption of goods and services; includes inflation, economic indicators or characteristics, labor market conditions, and economic aspects(Buffalo)

4.The study of the costs and cost effectiveness of healthcare practices(Duke)

5.the science that deals with the production, distribution, and consumption of wealth, and with the various related problems of labor, finance, taxation, etc. (Webster's New World)

6.Economics is the social science that studies the production, distribution, and consumption of goods and services. The word 'economics' is from the Greek for (oikos: house) and ν?μος (nomos: custom or law), hence "rules of the house(hold)." (wikipedia
)

7.The study of how people use their limited resources in an attempt to satisfy unlimited wants.(firstdata.com)

8.The study of how people, individually and in groups (families, businesses, governments, organizations) choose to use their relatively scarce productive resources to satisfy their wants.(mdk12.org)

9.External storage holds large volumes of data at reasonable cost.(Microsoft)

10.A theoretical science which provides a comprehension of the meaning and relevance of purposive (conscious) human actions. It is not about things and material objects; it is about the meanings and actions of men(mises.org)

11.Organizations that conduct research in the area of social science that involves the systematic study of the production, conservation and allocation of resources in conditions of scarcity, together with the organizational frameworks related to these processes.(urban.org)

12.research on such factors as interest rates, gross national product, inflation, unemployment, and inventories, as tools to predict the direction of the economy(frb.org)

13.The study of how scarce resources are allocated among competing uses(Hackett)

14.Examines the allocation of scarce resources among competing wants. Explores the principles of supply and demand and how prices are determined.(in.gov)

15.The study of the distribution of scarce resources that have alternative uses. (This is from Thomas Sowell’s book Basic Economics which can be found on the reading list for those who are interested.)

16.The study of the production, distribution and use of wealth

17.is the means by which society uses human and natural resources in the pursuit of human welfare. As such, economics extends beyond the boundaries of a single organisation and is inextricably linked to both the environmental and social elements of sustainable development.

18.is a social science seeking to analyze and describe the production, distribution, and consumption of goods and services.
（Based on Google.com）