Let us examine each of these definitions in detail to understand the concept better:

WEALTH ECONOMICS OR CLASSICAL ECONOMICS:

• This school of economic thought originated during the late 18th and early 19th century
• The main proponent of this definition is Adam Smith also known as the ‘Father of Modern Economics’ and other Classical Economists like David Ricardo, Jean – Baptiste Say, John Stuart Mill, Thomas Malthus etc
•   According to Adam Smith Economics is concerned with An Enquiry Into Nature And Causes Of Wealth Of Nations
•  Adam Smith's The Wealth of Nations in 1776 is usually considered to mark the beginning of classical economics. The fundamental message in Smith's influential book was that the wealth of nations was based not on gold but on trade: That when two parties freely agree to exchange things of value, because both see a profit in the exchange, total wealth increases.
•  Classical economic theory is rooted in the concept of a laissez-faire economic market. A laissez-faire--also known as free--market requires little to no government intervention. (French phrase "laissez-faire," or "let it be.")
• This School of economic thought stresses that economies function most efficiently if everyone is allowed to pursue his or her self interest, in an environment of free and open competition
• This ensures economic resources are allocated according to the desires of individuals and businesses in the marketplace
• The fundamental principle of the classical theory is that the economy is self‐regulating when free of coercion. Adam Smith referred to this as a metaphorical "invisible hand", which refers to the notion that private incentives are aligned with society welfare maximization under certain competitive conditions.
• ·The phrase invisible hand was introduced by Adam Smith in his book 'The Wealth of Nations'. He assumed that an economy can work well in a free market scenario where everyone will work for his/her own interest
• The invisible hand refers to an unseen mechanism that maintains equilibrium between the supply and demand of resources
• J E Cairnes in his book, “The Character and Logical Method of Political Economy” said Economics deals with the phenomenon of wealth
• French economist J.B. Say  - Economics is science which treats of wealth
• The American Economist, F.A Walker is of the view that Economics is that body of knowledge which relates to wealth

In all these definitions, key position is assigned to WEALTH