Alfred Marshall

Economics 

“Economics is the study of man in the ordinary business of life”

“It is the study of mankind in the ordinary business of life. It enquires how he gets his income and how he uses it. In one view, it is a study of wealth and on other hands, it is part of the study of man. “

Profit

“Profit is the earning of management”.

National Income 

The labor and capital of a country, acting on its natural resources, produce annually a certain net aggregate of commodities, material and immaterial, including services of all kinds, and net income due on account of foreign investments must be added in. This is the true net National income or Revenue of the country or the national dividend.