Every scholar tends to define economics to suit his purpose, for instance,
Adam Smith (1776) defined economics as an enquiry into the nature and causes of the wealth of nations
John Stuart Mill defined economics as the practical science of production and distribution of wealth
Davenport defined it as the science that treats phenomenon from the standpoint of price.
Alfred Marshall, on his part, did not consider wealth as a means itself but rather a source of human welfare. Therefore he defined Economics as a study of mankind in the ordinary business of life.